Effect of ischemic preconditioning on vascular reactivity and calcium sensitivity in hemorrhagic shock rats

AIM: To investigate the effect of ischemic preconditioning (IPC) on vascular reactivity and calcium sensitivity during hemorrhagic shock. METHODS: Appropriate method of IPC was selected by observing the effect of different strategies of IPC on the survival time and the survival rate in hemorrhagic shock rats. The effect of IPC on the pressor effect of norepinephrine (NE, 3 μg/kg) and the contractile response of superior mesenteric artery (SMA) to NE and calcium in vivo and in vitro were observed. RESULTS: Among 3 strategies of IPC, 3 cycles of abdominal aorta occlusion for 1 min and loosing for 5 min increased the survival time and 24 h survival rate significantly, which was superior to the other two IPC methods. In vivo, IPC significantly increased the pressor response to NE and the contractile response of SMA to NE (P<0.01). In vitro, IPC significantly improved the reactivity of SMA to NE and Ca²⁺. The E_max values of SMA to NE and Ca²⁺ in IPC group were significantly higher than that in shock control group (P<0.01). CONCLUSION: Ischemic preconditioning reverses Shock-induced vascular hyporeactivity via improving calcium sensitivity of the vasculatures.     

Positive inotropic action of urocortin on isolated heart tissues of the spontaneously hypertensive rat

AIM:To study the effects of urocortin (Ucn) on the isolated heart tissues of spontaneously hypertensive rat (SHR). METHODS:Effects of Ucn on contractile force and heart rate were observed in the SHR and Wistar rat right atrium, left atrium and right ventricle strip. RESULTS:Ucn (1-10 nmol/L) concentration-dependently increased the contractile force in the SHR and Wistar rat isolated right atrium. Ucn increased the contractile force in the SHR by (31.1±14.9)% at 3 nmol/L and by (65.7±22.4)% at 10 nmol/L, and its inotropic effect was significantly greater than that in Wistar rat (P<0.01) at the same concentration. Ucn (1-10 nmol/L) concentration-dependently increased the contractile force in the SHR and Wistar rat isolated left atrium, this effect had no difference between SHR and Wistar rat. No effect of Ucn on the heart rate of the isolated right atrium and on the contractile force of the isolated right ventricle strip was observed. CONCLUSION:The results indicate that the inotropic responses to Ucn in SHR are significantly greater than those in Wistar rats, suggesting that the change in heart function related with Ucn in SHR may have an important role in the pathophysiology of the hypertension.     

Role of Rho kinase in blocking the return of mesenteric lymph to improve vascular calcium sensitivity in hemorrhagic shock rats

AIM: To observe the role of Rho kinase in mesenteric lymph duct ligation or mesenteric lymph drainage to improve vascular calcium sensitivity in the rats subjected to hemorrhagic shock. METHODS: Male Wistar rats were randomly divided into sham group, shock group, shock+ligation (shock plus mesenteric lymph duct ligation) group and shock+drainage (shock plus mesenteric lymph drainage) group. After induction of shock (hypotension at 40 mmHg) for 3 h, the vascular rings of superior mesenteric artery (SMA) were prepared and used to measure the response to gradient calcium ions for determining the calcium sensitivity with a wire myograph system. In shock+ligation group and shock+drainage group, the vascular rings were incubated with Rho kinase agonist angiotensinⅡ or antagonist fasudil before the measurement of the response to gradient calcium ions. RESULTS: The calcium sensitivity of vascular rings in shock group was significantly lower than that in sham group, and that in shock+ligation group and shock+drainage group was significantly higher than that in shock group, but still lower than that in sham group. AngⅡ elevated the contractile activity of the vascular rings in response to gradient calcium ions and the pD₂, and fasudil significantly decreased the response to gradient calcium ions and E_max in shock+ligation group and shock+drainage group. At the same time, fasudil decreased the pD₂ in shock+ligation group. CONCLUSION: Rho kinase plays an important role in blocking shock mesenteric lymph return that improves calcium sensitivity.     

Effects of short-chain acyl-CoA dehydrogenase on hypertensive vascular remodeling

AIM: To investigate the changes of short-chain acyl-CoA dehydrogenase (SCAD) in hypertensive vascular remodeling and to explore the relationship between SCAD and vascular remodeling in hypertension.METHODS: The spontaneously hypertensive rats (SHR; 24 weeks old) and Wistar rats (24 weeks old) were used as experimental control groups. The SHR and Wistar rats of 16 weeks old were trained by swimming as experimental groups. The systolic pressure was measured periodically. The thickness of vascular wall and the diameter of the vascular lumen were measured. The contents of ROS and ATP, the enzyme activity of SCAD, and the expression of SCAD at mRNA and protein levels in the aorta were determined. The free fatty acid in the serum and aorta was also measured.RESULTS: Compared with Wistar group, the diameter of vascular lumen decreased in SHR group. The thickness of vascular wall, the ratio of vascular wall and the diameter of vascular lumen, and the blood pressure in SHR group were increased significantly (P<0.05). Compared with SHR group, the diameter of vascular lumen increased in SHR+swim group. The thickness of vascular wall, the ratio of vascular wall and the diameter of vascular lumen, and the blood pressure in SHR+swim group were decreased significantly. Compared with control group, the expression of SCAD at mRNA and protein levels, the enzyme activity of SCAD, and the content of ATP were decreased in SHR group. However, the free fatty acid in the serum and aorta, and the content of ROS in the aorta were increased in SHR group. The expression of SCAD at mRNA and protein levels, the enzyme activity of SCAD, the content of ATP were increased in Wistar+swim group and SHR+swim group. However, the free fatty acid in serum and aorta, and the content of ROS in the aorta were decreased in Wistar+swim group and SHR+swim group.CONCLUSION: Decrease in SCAD expression may be associated with hypertensive vascular remodeling. Swimming training can reverse hypertensive vascular remodeling by increasing the expression of SCAD in the aorta.     

Blockage of mesenteric lymph return promotes the vascular reactivity and calcium sensitivity in hemorrhagic shock rats

AIM: To observe the effects of mesenteric lymph duct ligation and mesenteric lymph drainage on the vascular reactivity and calcium sensitivity in hemorrhagic shock (HS) rats, and to investigate the role of mesenteric lymph on the vascular hyporeactivity during shock. METHODS: Seventy-two male Wistar rats were randomly divided into sham group (only operation), shock (duplicating HS model) group, shock+ligation group (duplicating HS model and mesenteric lymph duct ligation) and shock+drainage group (duplicating HS model and mesenteric lymph drainage). The changes of mean artery pressure (MAP) after injection of norepinephrine (NE, 3 μg/kg) at different time points were recorded. After hypotension (40 mmHg) for 3 h, the vascular ring of superior mesenteric artery (SMA) was made for determining the vascular reactivity and sensitivity to calcium by observing the contraction initiated by NE and Ca²⁺ under depolarizing conditions (120 mmol/L K⁺) in the isolated organ perfusion system. Meanwhile, the effects of angiotensin Ⅱ (AngⅡ) and insulin (Ins) on the vascular reactivity were also observed. RESULTS: Compared to sham group, the △MAP in shock group was increased significantly at 0 h and 0.5 h after shock, and that was decreased markedly at 1.5 h, 2 h, 2.5 h and 3 h after shock, respectively, and that in shock+ligation group and shock+drainage group was increased at 0 h, 0.5 h and 1 h after shock, decreased at 2.5 h and 3 h after shock, respectively. The △MAP in shock+ligation group and shock+drainage group was higher than that in shock group at 0.5 h after shock and all the time points followed. The SMA reactivity to NE and sensibility to Ca²⁺ in shock group, shock+ligation group and shock+drainage group were lower markedly than those in sham group. The vascular reactivity and calcium sensitivity in shock+ligation and shock+drainage groups were higher than those in shock group. The vascular reactivity and calcium sensitivity in shock group, shock+ligation group and shock+drainage group were lower than those in sham group, and those in shock+ligation and shock+drainage groups were increased as compared to shock group, respectively. CONCLUSION: Blockage of mesenteric lymphatic return with the methods of mesenteric lymph duct ligation and mesenteric lymph drainage promotes the vascular reactivity of HS rats. The mechanism may be related to improving the calcium sensitivity in the vasculature.     

Regulatory mechanism of Cx40 and Cx43 on endothelium-dependent vascular contractile reactivity in rat superior mesenteric artery

AIM: To investigate the regulatory mechanism of Cx40 and Cx43 on endothelium-dependent vascular contractile reactivity and calcium sensitivity following hemorrhagic shock in rats. METHODS: The rat superior mesenteric arteries (SMAs) were isolated and vascular rings were prepared. Transfection of Cx40 and Cx43 antisense oligodeoxyribonucleotide (Cx40 and Cx43AODN) was conducted to block the expressions of Cx40 and Cx43 in SMAs. The changes of contractile response, calcium sensitivity, the activity of myosin light chain phosphatase (MLCP) and myosin light chain kinase (MLCK), 20kD myosin light chain (MLC₂₀) phosphorylation in hypoxia treated SMA were observed. RESULTS: Cx40AODN decreased the activity of MLCP, increased the MLC₂₀ phosphorylation, by which Cx40AODN improved the calcium sensitivity and the contractile response of SMA. Cx43AODN increased the activity of MLCP, reduced the MLC₂₀ phosphorylation, by which Cx43AODN depressed the calcium sensitivity and the contractile response of SMA. No effect of Cx40 and Cx43AODN on the MLCK′s activity of SMA was observed. CONCLUSION: The mechanism that Cx40 and Cx43 regulates endothelium-dependent vaso-contractile responses following hemorrhagic shock may be mainly through regulating the activity of MLCP and MLC₂₀ phosphorylation in vascular smooth muscle cells.     

Mechanism of RhoA on vascular reactivity following hemorrhagic shock in rats

AIM: To observe the mechanisms of RhoA on vascular reactivity following hemorrhagic shock (HS) in rats. METHODS: The superior mesenteric artery (SMA) in rats subjected to hemorrhagic shock was adopted to assay the vascular reactivity via observing the contraction initiated by norepinephrine (NE) with isolated organ perfusion system. Meanwhile, the effects of Rho kinase, myosin light chain phosphatase (MLCP), myosin light chain kinase (MLCK) on RhoA regulating vascular reactivity were observed. The effects of RhoA agonist U-46619 and inhibitor C3 enzyme on the activities of Rho kianse, MLCP, MLCK and phosphorylation of MLC20 in the vascular smooth muscle cells (VSMC) with hypoxia were also measured. RESULTS: As compared to control group, the cumulative dose-response curves of SMA to NE at 2 h after shock shifted to the right, the maximal contractions (Emax) of NE was significantly decreased. RhoA agonist U-46619 increased the vascular reactivity in the late period of shock. C3 enzyme abolished U-46619 induced the increase in the contractile response of SMA to NE. Rho kinase inhibitor Y-27632 decreased U-46619-induced the increase in the vascular reactivity, MLCP inhibitor calyculin further promoted the increase in the vascular reactivity. However, MLCK inhibitor had no effect on the U-46619-induced change of vascular reactivity. After hypoxia, the activities of Rho kinase and MLCK, and the level of MLC20 phosphorylation were decreased, MLCP activity was increased. RhoA agonist U-46619 increased the activity of Rho kinase and phosphorylation of MLC20, decreased the activity of MLCP, but had no effects on MLCK activity. CONCLUSION: RhoA plays an important role in the regulation of vascular reactivity following shock. The mechanism is closely related to regulating the activities of Rho kinase and MLCP, and increasing the phosphorylation of MLC20 in VSMC.     

Production and distribution of endogenous sulfur dioxide and its generating enzyme in rats

AIM: To investigate the distribution of endogenous sulfur dioxide (SO2) and its generating enzyme (glutamate oxaloacetate transaminase, GOT) in normal rats. METHODS: Wistar rats were anaesthetized and heart, liver, lung, kidney and vascular tissues (including aorta and pulmonary, mesenteric, kidney and tail arteries) were isolated rapidly. SO2 content was determined by reverse-phase HPLC with fluorescence detection and GOT was detected in various tissues by quantitative real-time RT-PCR and enzymatic methods. GOT mRNA expression in arteries was studied through in situ hybridization. RESULTS: SO2 was endogenously generated in various rat tissues, including heart, liver, lung, kidney and arteries. The SO2 content was higher in arteries than that in other tissues. GOT enzyme and GOT mRNA expression were higher in heart, liver and kidney than those in arteries, and GOT1/GOT2 mRNA located in endothelia and vascular smooth muscle cells near endothelial layer. CONCLUSION: SO2 is endogenously generated in cardiovascular system, and the SO2 content in arteries is higher than that in other organs. GOT enzyme and GOT mRNA expression are low in arteries, and this phenomenon may be related with local metabolism.     

Role of PKC-α and δ isoforms in AVP improved contractile response of VSMC after hypoxia and its relations to MLC20 phosphorylation

AIM:The present study was to investigate the roles of protein kinase C α and δ isoforms (PKC-α, δ) in arginine vasopressin (AVP) improved contractile response of vascular smooth muscle cells (VSMC) to norepinephrine (NE) after hypoxia and its relations to myosin light chain (MLC₂₀) phosphorylation, myosin light chain phosphatase (MLCP) and myosin light chain kinase (MLCK) activity.METHODS: Primary cultures of VSMC were obtained from the superior mesenteric artery (SMA) of rats by explanting technique and the cells in third to fifth passage were used in the study. The effects of PKC-α and δ antagonists on AVP induced contractile response of VSMC to NE after 1.5 h hypoxia were observed by measuring the ratio of accumulative infiltration of fluorescent isothiocyanate-conjugated bovine serum albumin with transwell, and their effect on the activity of MLCP/MLCK in VSMC was assayed by enzymatic catalysis. At the same time, with the SMA from hemorrhagic shock rats (30 mmHg for 2 h), the effects of PKC α and δ isoforms in the regulation of AVP on MLC₂₀ phosphorylation of SMA after shock were observed by Western blotting.RESULTS: G 6976 (5×10^-6 mol/L, PKC-α isoform inhibitor) significantly antagonized AVP (5×10^-10 mol/L)-induced increase in the contractile response of VSMC to NE after hypoxia, and rottlerin (10^-5 mol/L, PKC-δ isoform inhibitor) also partly inhibited this effect. Hypoxia resulted in a significant increase in MLCP activity, with a decrease in MLCK activity of VSMC, and at the same time, the MLC₂₀ phosphorylation of SMA following hemorrhagic shock was significantly decreased. AVP inhibited the activity of MLCP and increased the phosphorylation of MLC₂₀, which was inhibited by G 6976, while rottlerin treatment only showed a slightly inhibitory effect. AVP and PKC-α, δ inhibitor had no significant influence on MLCK activity.CONCLUSION:AVP up-regulates vascular reactivity and calcium sensitivity of VSMC possibly through inhibiting the activity of MLCP and increasing the phosphorylation of MLC₂₀ by PKC-α isoform.     

Signal pathway of Cx40/43 regulates vascular contractile reactivity of superior mesenteric artery under hypoxic condition

AIM: To investigate the effect of connexin 40/43(Cx40/43) on cyclic adenosine monophosphate-protein kinase A (cAMP-PKA), cyclic guanosine monophosphate-protein kinase G (cGMP-PKG) and diacylglycerol-protein kinase C (DG-PKC) signal pathways and the regulatory role on the vascular contractile reactivity. METHODS: Rat superior mesenteric arteries (SMA) were isolated. The vascular rings of SMA were prepared and treated with Cx40/43 antisense oligodeoxyribonucleotide (Cx40/43AODN). The changes of the concentration of cAMP, cGMP and DG, the activity of PKA, PKG and PKC, the contractile response of hypoxia treated SMA rings were observed. RESULTS: Cx40AODN decreased the concentrations of cAMP, cGMP and the activities of PKA and PKG, increased the level of DA, the activity of PKC and the endothelium-dependent contractile response in SMA. Cx43AODN increased the concentrations of cAMP, cGMP and the activities of PKA and PKG, decreased the level of DA, the activity of PKC and the endothelium-dependent contractile response in SMA. CONCLUSION: Cx40/43 regulates endothelium-dependent vasoconstrictor reactivity of SMA after hemorrhagic shock, which may be related to cAMP-PKA, cGMP-PKG and DG-PKC signal pathways.     

Mechanism of calcium sensitivity in lymphatic hypo-reactivity in hemorrhagic shock rats

AIM: To observe the changes of lymphatic reactivity to norepinephrine (NE) and calcium sensitivity in vitro in hemorrhagic shock (HS) rats. METHODS: Male Wistar rats were randomly divided into sham group (with only operation), HS group (duplicating HS model, and divided into shock 1 h and shock 2 h subgroups). The thoracic duct rings (n=48 in each group) were prepared for assaying the lymphatic reactivity to NE and calcium sensitivity by lymphatic tension measurement technique in vitro with isolated perfusion system. Meanwhile, the effects of angiotensin Ⅱ (Ang Ⅱ) and insulin (Ins) on lymphatic reactivity were also observed. RESULTS: Compared with sham group, the NE concentration-response curves in HS 1 h and HS 2 h groups, and calcium concentration-response curves in HS 2 h group were obviously shifted to right. The lymphatic reactivity to NE, contraction to calcium, maximum effect(E_max)and avidity index (pD₂) were markedly reduced. In HS group, after incubating with calcium sensitizer Ang Ⅱ, the lymphatic reactivity to NE and calcium sensitivity were significantly increased but reduced in sham group. However, calcium sensitivity inhibitor Ins decreased the lymphatic contractile response to NE and Ca²⁺. CONCLUSION: The lymphatic hypo-reactivity in hemorrhagic shock rats is related to calcium desensitization, indicating a mechanism of lymphatic hypo-contraction.     

Changes of lymphatic vessel response to norepinephrine in hemorrhagic shock rats

AIM: To observe the changes of lymphatic vessel response to norepinephrine (NE) in hemorrhagic shock (HS) rats, and to explore the role of lymphatic reactivity in the pathogenesis of shock. METHODS: The lymphatic vessel pressure was observed through intubating into abdomen thoracic duct in 8 rats in sham group and HS group (which was bled from femoral artery until the mean arterial pressure to 40 mmHg). The changes of lymphatic vessel pressure response to NE at different time points were observed by injection of NE (5 μg/kg) through femoral vein. The spontaneous contraction frequency (F), maximal contraction diameter (a), maximal diastolic diameter (b) and static diameter (c) of mesenteric lymphatic (ML) living samples in 8 rats of each group were recorded through microcirculation video systems continuously. The changes of lymphatic fractional contraction index (index I), total contractile activity index (index II) and lymphatic dynamic index (LD-index) (to show the value using △F, △index I, △indexⅡ, △LD-index) were calculated after injection of NE at different time points. RESULTS: The changes of lymphatic boosting pressure response to NE in HS group was started to diminish 30 min after shock, and showed a progressive decreasing trend which significantly reduced than that in sham group at all time points of shock 1 h-3 h. In HS group, the △F, △indexⅡ, △LD-index at shock 1 h, the △F, △index I, △indexⅡ, △LD-index at shock 1.5 h and 2 h were significantly lower than those in sham group, and the △F, △index I, △indexⅡ, △LD-index at all time points were significantly decreased as compared to the values of pre-shock. CONCLUSION: Lymphatic vessel reactivity in shock rats is progressive declined in the process of hemorrhagic shock. The lymphatic vessel hypo-reactivity might play an important role in the pathogenesis of shock.     

Mesenteric lymph reperfusion exacerbates brain injury in superior mesenteric artery occlusion shock rats

AIM: To observe the effect of mesenteric lymph reperfusion (MLR) on the brain morphology and neurotransmitter in rats with superior mesenteric artery occlusion (SMAO) shock, and to explore the mechanism of oxygen free radicals, nitric oxide (NO), polymorphonuclear neutrophils (PMN), membrane ATPase function and energy metabolism. METHODS: Twenty-four male Wistar rats were randomly divided into 4 groups: in sham group, the rats were given only anesthetization and operation; in MLR group, the rats were performed 1 h occlusion of mesenteric lymphatics (ML) followed by 2 h of reperfusion; in SMAO group, the rats were performed 1 h occlusion of superior mesenteric artery (SMA) followed by 2 h of reperfusion; in MLR+SMAO group, the rats were performed 1 h occlusion of SMA and ML followed by 2 h of reperfusion. After 2 h of reperfusion, the brain tissue was taken for preparing microscopic sections to observe the morphological change. At the same time, the brain tissue was homogenized for determining the choline acetyltransferase (ChAT), acetylcholine esterase (AChE), dopamine (DA), norepinephrine (NE), lactic acid (LA), malondialdehyde (MDA), superoxide dismutase (SOD), NO, nitric oxide synthase (NOS), myeloperoxidase (MPO), cell membrane ATPase and ATP. RESULTS: Morphological observation showed that the architecture of the brain was close to normal in sham and MLR groups. Necrosis, degeneration and occasional swelling were found in neuronal cells in SMAO group, and in MLR + SMAO group the injury of the neurons was more serious than that in SMAO group. The contents of MDA, NO and LA, the activities of AChE, NOS and MPO in brain homogenate in SMAO and MLR+SMAO groups were increased, the ChAT activity and DA, NE contents were reduced significantly than those in MLR and sham groups, respectively. The contents of MDA and NO, the activities of AChE, NOS and MPO in MLR+SMAO group were higher than those in SMAO group. The activities of Na+-K+-ATPase and SOD in brain homogenate in SMAO group were lower than those in sham and MLR groups, the Mg2+-ATPase activity and ATP content were lower than those in MLR group. The activities of SOD, Na+-K+-ATPase, Ca2+-ATPase, Mg2+-ATPase and Ca2+-Mg2+-ATPase in brain homogenate in MLR+SMAO group were lower than those in sham and MLR groups, and the DA, Ca2+-ATPase, Mg2+-ATPase, Ca2+-Mg2+-ATPase and ATP were also lower than those in SMAO group. CONCLUSION: MLR exacerbates the brain injury, reduces the DA level and increases the AChE activity in SMAO shock rats, indicating that MLR enhances the brain tissue free radical injury, NO synthesis and releases, PMN detention, and decreases the activity of cell membrane ATPase, also induces the energy metabolism dysfunction.     

Effects of sesamin on blood fat,blood glucose and vascular remodeling in rats fed with high-fat and refined-sugar diet

AIM: To explore the effect of sesamin on blood fat, blood glucose and vascular remodeling in rats fed with high-fat, refined-sugar diet. METHODS: A high-fat, refined-sugar diet was given to rats for 24 weeks. Sesamin (120, 60, 30 mg·kg-1·d-1) was given by intragastric administration to the rats at 9th week, which lasted for 16 weeks. After 24 weeks, blood glucose, blood fat, blood pressure, activity of total anti-oxidation capacity (T-AOC) and concentration of hydrogen peroxide in serum and aorta were determined. Changes of histology and collagen fibers were observed in aorta by HE and Masson staining, respectively. Immunohistochemical method was used to examine iNOS protein expression in aorta. In mesenteric arteries, media thickness (M), luminal radius (L) and ratio of media to lumen (M/L) were measured. RESULTS: Compared to model group, sesamin (120, 60 mg·kg^-1·d^-1) obviously decreased the levels of blood glucose, blood fat, blood pressure and concentration of hydrogen peroxide in serum and aorta. Sesamin also markedly enhanced the activity of T-AOC in serum and aorta and reduced collagen deposition and iNOS protein expression in the vascular wall. In addition, proliferation of intima and vascular smooth muscle cells were improved. In mesenteric arteries, sesamin lessened M and M/L and increased L of mesenteric arteries. CONCLUSION: Sesamin ameliorates disorders of glucose and lipid metabolism and inhibits vascular remodeling in rats caused by chronic high-fat, refined-sugar diet.     

Functional changes of perivascular adipose tissue in hypertensive rats and the effects of statins therapy

AIM:To study the functional changes of perivascular adipose tissue (PVAT) in SHR and the effects of statins therapy.METHODS:Adult SHR at 10 weeks of age were treated with atorvastatin (50 mg·kg-1·d-1) or Xuezhikang (2 400 mg·kg-1·d-1) for 16 weeks.Age-matched untreated SHR and WKY were used as controls.Tail-cuff systolic blood pressure (SBP) was measured at the beginning and the end of experiment.Thoracic aorta was divided into two segments: vessel without PVAT ［Fat (-)］ and vessel with PVAT ［Fat (+)］.The differences in contractile force induced by phenylephrine in these vessels from the four groups of rats were compared.RESULTS:SBP in SHR was significantly higher than that in WKY at the beginning of the experiment.SBP of SHR treated with statins and WKY control did not show statistical difference during the treatment period.Contractile force of Fat(+) vessels in WKY and SHR groups treated with statins was lower than that in Fat(-) vessels.There was no difference in the contractile force between Fat(+) and Fat(-) vessels in SHR control.Bathing solution transferred from Fat(+) vessels in WKY,SHR-A,and SHR-X caused a relaxation response in Fat (-) vessels,but not in control SHR.CONCLUSIONS:PVAT in WKY released a transferable relaxation factor which attenuated the responsiveness of the vessels to phenylephrine.The release or the action of this relaxation factor was reduced in the SHR.Treatment with statins restored the release or the action of this relaxation factor in the SHR.     

Expression of ERK and MKP-1 in vascular smooth muscle of spontaneously hypertensive rats with different ages

AIM: To investigate the expression of mitogen- activated protein kinase and mitogen-activated protein kinase phosphatase-1 in thoracic aorta smooth muscles of spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) with different ages and the relationship between those and hypertension. METHODS: The caudal arterial pressure was measured by tail-cuff. Protein expression of p-ERK was detected by Western blotting, and MKP-1 mRNA in thoracic aorta smooth muscle was examined by RT-PCR. RESULTS: (1) The blood pressure of SHR was obviously higher than that of age-matched WKY (P<0.01), elevated with age (P<0.05) and became stable from 14-week-old. (2) The expression of p-ERK and MKP-1 in SHR was higher than that in WKY in 5-week-old rats, and the expression of p-ERK increased with age, while the expression of MKP-1 decreased with age (P<0.05). CONCLUSION: MKP-1 may play an important role in the development of hypertension in SHR. The decrease in the expression of MKP-1 that resulted in the activation of MAPK may induce vascular smooth muscle proliferation and hypertrophy.     

Comparison of vascular remodeling between small artery and aorta in spontaneous hypertensive rats

AIM: To examine the difference of vascular remodeling between aorta and small artery in sponta-neous hypertensive rats (SHR) and control rats.METHODS: Male SHR (20-week-old) were used as experiment group, and age matched male Wistar-Kyoto (WKY) rats were used as control group. The systolic blood pressure and body weight were measured once a week. At 43 weeks old, the rats were anaesthetized, blood samples were collected, and thoracic aorta and mesenteric small artery tissue were harvested. The morphological changes of the arterial tissue were observed with HE staining. The collagen and elastine fibers were detected by the Sirius red-Victoria blue staining. The protein expression of type I and Ⅲ collagens were analyzed by confocal laser-scanning microscopy and Western blot. The changes of the vascular ultrastructure were imaged by transmission electron microscopy. The expression of proliferating cell nuclear antigen (PCNA) and the cell apoptosis in the arterial wall were examined by immunohistochemical method and TdT-mediated dUTP nick and labeling (TUNEL) detection.RESULTS: The inner diameter (ID) and luminal cross-sectional area (LCSA) of mesenteric small artery were decreased, whereas ratio of wall thickness (WT) to ID (WT/ID) and ratio of wall cross-sectional area (WCSA) to LCSA (WCSA/LCSA) were increased. Meanwhile, adventitia fibroblast migrated to the media, with overload collagens, especially collagen Ⅲ. Proliferation index (PI) and apoptotic index (AI) of the mesenteric small artery wall cells were increased. The ID, LCSA, WT/ID and WCSA/LCSA of the aorta were increased. Moreover, the vascular smooth muscle cells (VSMCs) showed hypertrophy and hyperplasia, with overload collagens. The PI and AI of the aortic wall cells were increased.CONCLUSION: The difference of vascular remodeling between the aorta and small artery is significant. The small artery mainly appears hyperplasia of matrix, especially the adventitial collagen Ⅲ. Meanwhile, the cell apoptosis in the small artery wall is increased. The aorta mainly appears hyperplasia and hypertrophy of media VSMCs.     

Effect of asymmetric dimethylarginine on blood pressure and renal function in sympathectomized spontaneously hypertensive rats

AIM: To investigate the effect of asymmetric dimethylarginine (ADMA) on blood pressure and renal function in sympathectomized spontaneously hypertensive rats (SHR). METHODS: The neonatal SHR were sympathectomized by guanethidine monosulfate. Systolic and diastolic blood pressure was monitored by tail-cuff method. Urine excretion of norepinephrine (NE) was measured by metabolic cage collection. The levels of ADMA and NE in the kidneys were analyzed by HPLC. Nitric oxide (NO) content in SHR kidney was detected by colorimetry. The protein expression of endothelial nitric oxide synthase (eNOS) was determined by Western blot. Glomerular filtration rate (GFR) was examined to evaluate the renal function. RESULTS: Neonatal chemical sympathectomy produced significant decreases in urinary NE excretion, renal NE and ADMA contents, and systolic and diastolic blood pressure compared with the sympathetically intact SHR (P<0.05). Moreover, the level of NO content and protein expression of eNOS in the kidneys were significantly increased (P<0.05). However, no significant difference was observed in microalbumin, urinary sodium excretion and GFR between the sympathetically intact SHR and the sympathectomized SHR. CONCLUSION: Inhibition of sympathetic nervous system affects blood pressure by reducing the release of ADMA and NE, and increasing NO synthesis and eNOS expression. The regulation of ADMA generation by sympathetic nervous system does not influence renal function.     

Effect of fluvastatin on migration of vascular smooth muscle cells from rats

AIM: To investigate the effect and mechanism of fluvastatin on the migration induced by platelet derived growth factor-BB (PDGF-BB) and endothelin-1 (ET-1) in cultured vascular smooth muscle cells (VSMCs). METHODS: Cultured VSMCs derived from spontaneously hypertensive rats (SHR) were used. Cell migration was determined by modified Boyden chamber assays. Intracellular free calcium (［Ca2+］i) was measured with fluorescent Ca2+ indicator Fura-2/AM. RESULTS: PDGF-BB and ET-1 significantly induced VSMCs migration, which was inhibited by pretreatment of VSMCs with fluvastatin (10-9-10-5 mol/L) in a dose-dependent manner, and the peak inhibition rate of migration induced by PDGF-BB and ET-1 was over 86.67%. Fluvastatin also attenuated the increase in ［Ca2+］i induced by PDGF-BB and ET-1, with a peak inhibition rate of 86.76% and 65.32%, respectively. CONCLUSION: PDGF-BB and ET-1 promote migration of VSMCs from SHR．Fluvastatin may have direct inhibitory effects on cell migration induced by PDGF-BB and ET-1. The increase in ［Ca2+］i may acts as intracellular signaling in the migration in response to PDGF-BB and ET-1 in VSMCs.     

Pinacidil pretreatment increases vascular reactivity and calcium sensitivity after hemorrhagic shock

AIM: To observe the protective effects of protein kinase Cα(PKCα) and protein kinase Cε(PKCε) activated by pinacidil pretreatment on vascular reactivity and calcium sensitivity after hemorrhagic shock in rats. METHODS: The changes of the pressor effect(the change of mean arterial pressure) and vasoconstriction response(the changes of diameter) of superior mesenteric artery(SMA) to norepinephrine(NE) were observed. The vascular reactivity and calcium sensitivity of the first class arborization of SMA induced by pinacidil pretreatment with different volume and at different time points before shock were determined. The effects of PKCα and PKCε antagonists on the protection of pinacidil pretreatment, and the effects of pinacidil pretreatment on the translocation of PKCα and PKCε were also measured. RESULTS: (1) The pressor effect and vasoconstriction response of SMA to NE, and the vascular reactivity and calcium sensitivity of the first class arborization of SMA in 2 h shock group were significantly decreased as compared to those in normal controls(P<0.01). Pinacidil(25 μg/kg) pretreated at 30 min before shock attenuated the above changes.(2) The inhibitors of PKCα and PKCε suppressed the protective effects of pinacidil pretreatment(25 μg/kg pinacidil pretreated at 30 min before shock) on the vascular reactivity and calcium sensitivity. The E_max of NE was decreased by 42.9% and 62.9%, respectively(P<0.01). The E_max of Ca²⁺ was decreased by 31.1% and 56.1%, respectively(P<0.01). Pinacidil(25 μg/kg) pretreated at 30 min before shock increased the protein expression of PKCα and PKCε on the membrane, and decreased the protein expression in the cytoplasm as compared to those in 2 h shock group(P<0.01). CONCLUSION: Pinacidil pretreatment activates PKCα and PKCε, and induces the increasing effects of vascular reactivity and calcium sensitivity after hemorrhagic shock in rats.