Estrogen treatment enhances mesenteric lymphatic contractility in rats after hemorrhagic shock

AIM To investigate the effects of 17β-estradiol （E2） treatment on the mesenteric lymphatic microcirculation and isolated lymphatic contractility in rats after hemorrhagic shock, and to explore the relationship between contractility and the difference between intra- and extracellular calcium ion concentrations （［Ca²⁺］） of lymphatic smooth muscle cells （LSMCs）. METHODS Male Wistar rats were divided into sham group, shock group and shock+E2 group. The rats were subjected to hemorrhage ［（40±2） mmHg for 90 min］ and resuscitation with or without subcutaneous injection of E2 （2 mg/kg）. After resuscitation for 3 h, the mesenteric lymphatic microcirculation in vivo was observed. Moreover, the isolated mesenteric microlymphatic rings were prepared for the observations of lymphatic contractility evaluated by the indexes including end-systolic diameter, end-diastolic diameter, contraction frequency （CF） and passive diameter. Meanwhile, the difference between intra- and extracellular ［Ca²⁺］ of LSMCs was recorded during lymphatic contraction. RESULTS Treatment with E2 significantly enhanced the CF, total contractile fraction and lymphatic dynamics index in vivo in the rats after hemorrhagic shock, and increased the CF, the fractional pump flow and the difference between intra- and extracellular ［Ca²⁺］ of LSMCs in isolated lymphatics from the shocked rats （P<0.05）. CONCLUSION Estrogen treatment enhances lymphatic contractility in rats after hemorrhagic shock, which is related to enhancement of difference between intra- and extracellular ［Ca²⁺］ of LSMCs.     

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.     

The disturbance of calcium metabolism of vascular smooth muscle in the late phase of septic shock and the underlying mechanism

AIM: To evaluate the alterations in calcium metabolism of the vascular smooth muscle in the late phase of septic shock and test the hypothesis that nitric oxide might be involved in sepsis-induced vascular hyporeactivity. METHODS: Male Sprague-Dawley rats were subjected to sepsis by cecal ligation and puncture (CLP). 18 hours post CLP, rat aortic rings were employed for measurement of contractile responses by using organ bath technique. RESULTS: In endothelium-denuded aortic rings from CLP rats, concentration-contraction curves to phenylephrine (PE) and KCl were significantly decreased when compared to that from sham control rats. The transient contraction induced by PE in calcium-free Krebs solution and the concentration-dependent contraction to CaCl₂ in KCl-depolarized medium were also markedly reduced. The hyporeactivity was partially reversed by treatment with aminoguanidine, a selective inducible nitric oxide synthase inhibitor. CONCLUSION: An impairment in calcium handling in vascular smooth muscle is involved in the vascular hyporeactivity during the late phase of septic shock, in which an excessive nitric oxide production might be the major mechanism.     

The signal transducers involved in the regulation of calcium sensitivity of vascular smooth muscle in hemorrhagic shock

AIM: To observe the regulatory effects of Rho-kinase, PKC and PKG on calcium sensitivity of vascular smooth muscle in hemorrhagic shock in rats. METHODS: The superior mesenteric artery (SMA) from hemorrhagic shock model of rat was adopted to assay the calcium sensitivity via observing the contraction initiated by Ca2+ under depolarizing conditions (120 mmol/L K+) with isolated organ perfusion system. Rho-kinase agonist Ang-Ⅱ and inhibitor fasudil, PKC agonist PMA and inhibitor staurosporine, PKG agonist 8Br-cGMP and inhibitor KT-5823 were used as tool agents to study the regulatory effect of Rho-kinase, PKC and PKG on the calcium sensitivity of SMA following shock. RESULTS: Ang-Ⅱ, PMA and KT-5823 improved the calcium sensitivity of SMA and made the cumulative dose-response curve of SMA to Ca2+ shift to the left, their Emax of Ca2+ (at 3×10-2 mol/L) was 0.630 g/mg, 0.595 g/mg and 0.624 g/mg, respectively, which were all higher than that in shock control (0.377 g/mg) (P<0.05, P<0.01). Fasudil, staurosporine and 8Br-cGMP delimitated the calcium sensitivity of SMA and made the cumulative dose-response curve of Ca2+ shift to the right, their Emax at 3×10-2 mol/L of Ca2+ was 0.242 g/mg, 0.230 g/mg and 0.256 g/mg, respectively, which were all lower than that in shock control (0.377 g/mg) (P<0.05, P<0.01). CONCLUSION: Rho-kinase, PKC, PKG play important roles in the regulation of calcium sensitivity of vascular smooth muscle in hemorrhagic shock.     

Role of myosin-light-chain kinase in biphasic contractile activity of lymphatics isolated from hemorrhagic shock rats

AIM: To elucidate the mechanism by which myosin-light-chain kinase (MLCK) modulates the biphasic contractile activity of lymphatics isolated from the rats subject to hemorrhagic shock (HS). METHODS: Male Wistar rats were randomiz to control group and HS group. In HS group, the rats were subject to HS and then further divided into HS 0 h, 0.5 h, 1 h, 2 h and 3 h subgroups. Thoracic ducts of control and shock rats were isolated and used to determine the protein levels of phosphorylated MLCK (p-MLCK). In addition, thoracic ducts obtained from control, 0.5 h- and 2 h-shocked rats were used to observe the contractile properties of lymphatics by a pressure myograph in vitro . Lymphatic rings were prepared and incubated with ML-7 (a specific inhibitor of MLCK) or substance P (SP, an agonist of MLCK). During the experiment, the contractile frequency (CF), end-diastolic diameter, end-systolic diameter and passive diameter in Ca²⁺-free PSS buffer were measured and used to calculate the lymphatic tonic index (TI), contractile amplitude (CA) and fractional pump flow (FPF) as the indexes of lymphatic contraction activity. RESULTS: The levels of p-MLCK in lymphatics in 0 h- and 0.5 h-shocked rats were significantly increased compared with the control rats, and it was gradually decreased with the development of shock. The values of CF, TI and FPF in 0.5 h-shocked lymphatics were significantly increased at transmural pressure of 1, 3 and 5 cmH₂O compared with those in control group, and significantly blunted by ML-7. SP obviously increased the suppressive effects induced by ML-7 and restored the values of CF, TI and FPF to the levels of HS 0.5 h group. CF, TI and FPF in 2 h-shocked lymphatics significantly declined under different transmural pressure as compared with those in control group, and significantly elevated by SP. Similarly, ML-7 depressed the effects of SP. No significant difference was found in CA between 0.5 h- and 2 h-shocked lymphatics. SP decreased the CA of lymphatics obtained from 2 h-shocked rats and this effect was suppressed by ML-7. However, both agents had no effects on CA of 0.5 h-shocked lymphatics. CONCLUSION: MLCK, as an essential enzyme that influences the contraction of lymphatic smooth muscle cells, involves in the modulation of biphasic changes of lymphatic contractile activity during the process of HS.     

Muscarinic receptor subtypes and gastrointestinal smooth muscle function

The muscarinic receptor family expressed in smooth muscle throughout the body is thought to be composed of five subtypes coupling to distinct signaling systems, respectively. The population in smooth muscle is composed of mainly M₂ and M₃ subtypes in a 80% to 20% mixture. The muscarinic receptor, mainly M₃ receptor, play an important role in regulating gastrointestinal smooth muscle contraction. Selective muscarinic M3 antagonist should have therapeutic utility in the treatment of gastrointestinal disease.     

Effects of She xiang bao xin wan (SXBXW) on phenotype transformation of vascular smooth muscle cells

AIM: To observe the effects of She xiang bao xin wan (SXBXW) of Chinese patent drug on the phenotype transformation of vascular smooth muscle cells.METHODS: The vascular smooth muscle cell line RASMC P8 was used as the cell model in this experiment. The cells were treated with SXBXW at the doses of 0.25 g/L, 0.50 g/L, 1.0 g/L and 2.0 g/L, respectively, and control cells were treated with the same volume of culture medium without SXBXW. The expression of α-smooth muscle actin (α-SMA) and the smooth muscle myosin heavy chain (SM-MHC), which served as specific molecular markers of vascular smooth muscle contraction in RASMC P8 cells, was analyzed by flow cytometry. RESULTS: The percentages of α-SMA and SM-MHC negative cells in SXBXW treated groups were lower than those in control group. Meanwhile, the percentages of α-SMA and SM-MHC positive cells were increased in RASMC P8 cells treated with SXBXW, indicating that SXBXW prompted the transformation of RASMC P8 cells from synthetic to contractile phenotype.CONCLUSION: Chinese patent drug SXBXW plays a role in transforming the cell phenotype from synthetic to the contraction in vascular smooth muscle.     

Effects of Tian ma gou teng decoction on the serum free calcium concentration and the L-type calcium channels in the vascular smooth muscle cells in spontaneously hypertensive rats

AIM: The research was to investigate the effects of the Tian ma gou teng decoction on the electric physiology feature of L-type calcium channels in the vascular smooth muscle cells in spontaneously hypertensive rats (SHR), and to further explain the mechanism of the Tian ma gou teng decoction in the intervention of blood pressure.METHODS: 12-week-old SHRs were assigned randomly into five groups：group A (treated with Tian ma gou teng decoction), group B (treated with Tian ma gou teng decoction with subtraction concha haliotidis), group C (treated with nifedipine), group D (treated with concha haliotidis), group E (treated with normal saline as control), each group consisted of 9 rats. After treatments were conducted for 4 weeks, the free calcium concentration in serum was measured. The electric physiology feature of L-type calcium channels in the vascular smooth muscle cells was analyzed by patch clamp technique (PCT).RESULTS: No significant difference between group A and group C was observed in the serum free calcium concentration (P>0.05). There were significant differences among group B, group D and group E (P<0.05), compared to before treatment, the change in group E was the most obvious. A decrease in the L-type calcium channel current of vascular smooth muscle cells was observed in group A and group C. The function of group D was feeble, no decrease in the L-type calcium channels current of vascular smooth muscle cells was observed in group B and group E.CONCLUSION: Tian ma gou teng decoction can increase the serum free calcium concentration and block the L-type calcium channel current in vascular smooth muscle cells, indicating one of the mechanism of intervention of blood pressure.     

Research progress on pacemaker function of interstitial cells of Cajal in gastrointestinal tract

Interstitial cells of Cajal (ICC) is the pacemaker in the gastrointestinal tract, which is closely associated with the formation of slow wave and the regulation of gastrointestinal motility. As the pacemaker of gastrointestinal tract, the activation of pacing signal is triggered by the local calcium oscillation in the ICC. The change of calcium concentration can activate many relevant ion channels, such as NSCC, ANO1, VGCC, HCN channels and potassium channels, which can generate a large number of pacing current to form the slow wave and then propagated by the gap junction between the ICC networks and smooth muscle cells to make the peristalsis of gastrointestinal tract in autonomic rhythm. However, the mechanism of these ion channels in the pacemaker activity is still unclear, so we refer to make a review about the research progress on these pacemaker channels in this article to illuminate the mechanism of pacemaker activity in ICC.     

Relationship between cell calcium ion transporter ryanodine receptor 3 and atherosclerotic plaque in apolipoprotein E gene-deficient mice

AIM:To investigate the change of cell calcium ion transporter ryanodine receptor 3(RYR3) in the aorta smooth muscle cells of apolipoprotein E gene-deficient(ApoE^-/-) mice, and to elucidate the relationship between RYR3 and atherosclerotic plaque in ApoE^-/- mice. METHODS:Six-week-old ApoE^-/- mice and wild-type C57BL/6J mice were used in the experiment. The animals were sacrificed for pathological observation at the time points of 20, 27 and 33 weeks after hyperlipidic diet, respectively. Four sections of the aortic root were prepared and HE and immunohistochemical staining were performed. All the sections were analyzed with a computer image analysis system. RESULTS:Compared with the controls, the expression of RYR3 was markedly lower in ApoE^-/- mice(P<0.05). As the age of ApoE^-/- mice increasing, the expression of RYR3 decreased significantly, and was negatively correlated to the plaque area corrected by lumen area(r＝-0.652, P<0.01). CONCLUSION:Cell calcium ion transporter RYR3 participates in the pathological process of atherosclerosis, and is closely related to the formation of atherosclerotic plaques.     

Effects of new cannabis preparations O-1602 and cannabidiol on LPS-induced intestinal motility disorder in rodents

AIM: To investigate the therapeutic effects and related mechanisms of two new cannabis preparations, O-1602 and cannabidiol (CBD), on lipopolysaccharide (LPS)-induced rodent models of intestinal motility disorder in vivo and in vitro. METHODS: The animal model of intestinal motility disorder was induced by intraperitoneal injection of LPS in mice. The gastrointestinal transit was measured by gavaging charcoal marker. Western blotting was applied to evaluate the protein expression of G-protein-coupled receptor 55 (GPR55). Meanwhile, the levels of tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) were tested by ELISA to assess the inflammatory degree. Smooth muscle strips from the rat and mouse ileum were incubated with LPS in vitro to establish motility disorder, and both the spontaneous contraction and electrically-evoked contraction were recorded using the organ bath technique. The traditional intracellular microelectrode technique was used to record the changes of membrane potential of smooth muscle cells. The method of determining phosphorus content was applied to assay the Ca²⁺-ATPase activity in smooth muscle tissues. RESULTS: In vivo, LPS resulted in significant inflammation and the disorder of gut movement (P<0.01). Pretreatment with CBD decreased both the level of IL-6 (P<0.01) and the expression of GPR55 (P<0.01), and further improved the motility of gut movement (P<0.05). O-1602 and CBD selectively normalized LPS-induced spontaneous and electrically-evoked contraction disorder of intestinal smooth muscle strips of rats and mice in vitro (P<0.05 or P<0.01), but they had no effect on the membrane potential of the smooth muscle cells both in normal and pathophysiological states. CBD also decreased the elevated Ca²⁺-ATPase activity in smooth muscle tissues induced by LPS (P<0.05). CONCLUSION: In vivo, CBD shows protective effect on LPS-induced intestinal motility disorder by reducing inflammation and down-regulating GPR55 expression. O-1602 and CBD counterbalance LPS-induced intestinal motility disorder to some extent in vitro, and the possible mechanism may be involved in regulating the Ca²⁺-ATPase activity of smooth muscle tissues, but not including the change of membrane potential.     

Role of ZIPK in the regulatory effects of PKCα and PKCε on calcium sensitivity during hemorrhagic shock in rats

AIM: To observe the role of zipper-interacting protein kinase (ZIPK) in the regulatory effects of protein kinase Cα (PKCα) and protein kinase Cε (PKCε) on calcium sensitivity during hemorrhagic shock(HS) in rats. METHODS: The skinned first class arborization of superior mesenteric artery (SMA) from HS rats were adopted to observe the influence of inhibitor of ZIPK on the effects of PKCα and PKCε agonists on calcium sensitivity after shock via measuring the contraction initiated by Ca2+ with isolated organ perfusion system, hypoxic vascualr smooth muscle cells (VSMCs) were adopted to measure the protein expression and activity of ZIPK after applying PKCα and PKCε agonists following hypoxia via Western blotting. RESULTS: (1) The calcium sensitivity of SMA was decreased after 2 h shock, and increased by agonists of PKCα and PKCε. Emax of Ca2+ was increased from 47.2％to 66.5％ (P<0.01) and 66.3％ (P<0.01) of normal control respectively as compared with 2 h shock group. The increasing effects of PKCα and PKCε agonists on calcium sensitivity of SMA after 2 h shock were weakened by the inhibitor of ZIPK. The cumulative dose-response curve of Ca2+ was shifted to the right, the Emax of Ca2+ was decreased to 42.6％ and 47.5％ of normal control (P<0.01), respectively. (2) The protein expression and activity of ZIPK in VSMCs were decreased after 2 h hypoxia, and were increased by the agonists of PKCα and PKCε following 2 h hypoxia. CONCLUSION: PKCα and PKCε regulate the calcium sensitization probably through changing the protein expression and activity of ZIPK following HS in rats.     

Mechanism of quercetin improving rat coronary artery myogenic response under high glucose

AIM: To investigate the mechanism of quercetin improving rat coronary artery myogenic response under high glucose (HG) by measuring muscle tension of coronary arterial ring and recording voltage-gated K⁺ channel (Kv) current of coronary artery smooth muscle cells by whole cell patch clamp. METHODS: The coronary rings from the normal SD rats were acutely isolated, and then divided into 6 groups: (1) control group; (2) HG group; (3) HG+low dose (3 μmol/L) of quercetin group; (4) HG+moderate dose (10 μmol/L) of quercetin group; (5) HG+high dose (30 μmol/L) of quercetin group; (6) HG+C6303 (PKC inhibitor)+high dose of quercetin group. Determinations of coronary artery response to vasoconstrictor (60 mmol/L KCl or 0.1 mmol/L U46619) or vasodilator (ACh at 10^-9~10^-5 mol/L) were performed, and the percentage of coronary ring tension was calculated using the contraction as 100% caused by 60 mmol/L KCl. The rat coronary artery smooth muscle cells were acutely isolated for recording the Kv current using whole cell patch clamp. RESULTS: Compared with control group, the contraction amplitudes to 60 mmol/L KCl or 0.1 mmol/L U46619 were significantly increased under HG incubation. Quercetin intervention concentration-dependently reduced the coronary artery contraction amplitude. Incubation of PKC specific inhibitor C6303 attenuated the effect of quercetin. Compared with control group, the diastolic amplitude to ACh decreased significantly in HG group, and quercetin intervention concentration-dependently increased the coronary artery diastolic amplitude. Incubation of PKC specific inhibitor C6303 attenuated the effect of quercetin. Compared with control group, HG incubation inhibited Kv current of coronary artery vascular smooth muscle cells significantly, and quercetin intervention attenuated the inhibitory effect of HG on Kv current intensity. Incubation of PKC specific inhibitor C6303 attenuated the effect of quercetin. CONCLUSION: Quercetin has a protective effect on myogenic response of coronary artery under HG and the effects is related to the increase in Kv current and the activation of PKC in vascular smooth muscle cells.     

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.     

Relaxation effect of isoliensinine on isolated mouse airway smooth muscle

AIM: To study the relaxation effect of isoliensinine on high K⁺-induced isolated mouse airway smooth muscle (ASM) and the underlying mechanism. METHODS: The muscle tension transducer was used to detect the effects of isoliensinine on high K⁺-induced precontraction and Ca²⁺ influx in ASM. The technique of patch-clamp and calcium imaging system were respectively used to examine the effects of isoliensinine on LVDCC currents and[Ca²⁺]_i of the ASM cells (ASMCs). RESULTS: Isoliensinine significantly relaxed precontracted ASM induced by high K⁺ in a concentration-dependent manner. The maximum relaxation ratio was(95.3±3.9)% by isoliensinine at 100 μmol/L. In addition, LVDCC currents were measured using the whole-cell patch-clamp technique, which were abolished by isoliensinine. High K⁺-induced 340/380 nm fluorescence ratio of Fura-2 was 0.63±0.10 in ASMCs, while it decreased to 0.36±0.05 after the addition of isoliensinine (P<0.01). When isoliensinine was added at the peak point of[Ca²⁺]_i, the ratio rapidly decreased from 0.74±0.02 to 0.42±0.05 (P<0.01). Moreover, isoliensinine inhibited high K⁺-induced Ca²⁺ influx-mediated contraction of ASM. CONCLUSION: Isoliensinine inhibits LVDCC currents, terminates Ca²⁺ influx and reduces[Ca²⁺]_i, eventually resulting in relaxation of the ASM, indicating isoliensinine might be a potential bronchodilator.     

Ca2+-activated Cl- channels and pulmonary hypertension induced by high pulmonary blood flow

Pulmonary hypertension induced by high pulmonary blood flow involves a variety of complex mechanisms, including endothelial damage, pulmonary artery smooth muscle relaxation-contraction disorder and vascular remodeling. Besides, the factor of ion channels in pulmonary artery smooth muscle cells is also highly correlated to vasoconstriction. In recent years, many studies have shown that activation of Ca²⁺-activated Cl^- channels is responsible for the membrane depolarization of pulmonary artery smooth muscle cells, and plays an important role in the regulation of vascular tone and vasoconstriction. This article reviews the biophysical and pharmacological characteristics of Ca²⁺-activated Cl^- channels as well as the influence of Ca²⁺-activated Cl^- channels in high pulmonary blood flow-induced pulmonary hypertension.     

Changes of Ca2＋ activated potassium channels and cellular-proliferation in autogenous vein grafts

AIM: To investigate changes of Ca^2＋ activated potassium channels (K_Ca) in autogenous vein grafts. METHODS: The contraction of venous ring was measured by means of perfusion in vitro. The intimal proliferation and proliferation of cultured smooth muscle cells (vascular smooth muscle cells, VSMCs) were observed by the means of computerised image analysis and MTT method, respectively. Furthermore, whole cell mode of patch clamp was used to record K_Ca of VSMCs isolated from autogenous vein grafts. RESULTS: 1 week after transplantation there were no significant differences of contraction and intimal relative thickness between autogenous vein grafts and control. Contraction and intimal relative thickness of autogenous vein graft were significantly increased 2 weeks after transplantation (P＜0.05, n=8 vs control), and they were more enhanced 4 weeks after vein transplantation (P＜0.01, n=8 vs control). TEA (blocker of Ca^2＋ activated potassium channels) increased MTT A₄₉₀ value of VSMCs from femoral vein in a dose-dependent manner (P＜0.05, n=8). K_Ca current density was significantly attenuated in VSMCs from autogenous vein grafts 1-4 weeks after transplantation (P＜0.05, n=5). CONCLUSION: K_Ca was inhibited in autogenous vein graft, which accounted for vasospasm and intimal proliferation.     

Changes of large-conductance calcium-activated potassium channel in gastric smooth muscle cells of diabetic gastroparesis rats

AIM: To discuss the relevance between the pathogenesis of diabetic gastroparesis and the large-conductance calcium-activated potassium channels (BK_Ca) in gastric smooth muscle cells. METHODS: The SD rats were randomly divided into control group and model group. The gastric smooth muscle cells of the SD rats were enzymatically isolated in a low calcium solution containing papain. The current was recorded by patch clamp single channel recording technique. The expression of KCNMA and KCNMB1 were observed by the method of immunohistochemistry. RESULTS: The value of BK_Ca single channel conductance was (220.10±10.90) pS; the channels had distinct voltage dependent and calcium dependent characteristics. In outside-out patch (Vm =+30 mV), the activation of BK_Ca was blocked by 200 nmol/L IbTX completely. Compared with control group, the open probability and amplitude of current in model group significantly increased, while the mean open time and mean close time significantly decreased. Compared with control group, the expression of KCNMB1 in model group was significantly increased. CONCLUSION: Up-regulation of β1-subunit and increase in BK_Ca functional activities may be associated with diabetes gastroparesis in rats.     

Substance P enhances pump function of isolated lymphatics from hemorrhagic shock rats

AIM: To establish a technique of lymphatic perfusion in vitro and to determine the effect of substance P (SP) on lymphatic contractility during the process of hemorrhagic shock (HS). METHODS: Male Wistar rats were randomly divided into control group (surgical procedure only) and HS group . Thoracic ducts were isolated from HS rats at the corresponding time points. The segment of thoracic duct was prepared, perfused in vitro at the transmural pressure of 3 cmH₂O and stimulated with gradient concentrations of SP to measure the lymphatic contractile activity. The end-systolic diameter, end-diastolic diameter, contraction frequency (CF) and passive diameter of isolated lymphatics were measured. The contraction amplitude (CA), tonic index (TI) and fractional pump flow (FPF) were also calculated.RESULTS: SP increased lymphatic CF, TI and FPF, and the effects were enhanced with the increase in the concentration of SP. The CF, TI and FPF of 2 h- and 3 h- shocked lymphatics were elevated to/over the value of baseline levels before the experiment by SP at the concentration starting from 3×10^-8 mol/L. At the same concentration of SP, the CA of lymphatics showed no significant statistical difference among the groups. However, with the increase in SP concentration, the lymphatic CA had a downward trend in all groups.CONCLUSION: SP enhances the pump function of lymphatics not only under physiological condition, but also in shock during different stages.     

Progress of STIM1, a dynamic calcium signal transducer, #br# in cardiovascular diseases

Stromal interaction molecule 1 (STIM1) is a transmembrane protein of the endoplasmic reticulum (ER), a Ca²⁺ transducer in ER that activates the store-operated calcium channel. Through Orai1 protein, STIM1 adjusts the intracellular and extracellular calcium concentration. This way is called a store-operated Ca²⁺ entry. STIM1 plays a key role in phenotypic transformation of vascular smooth muscle cells, proliferation of endothelial cells, myocardial hypertrophy and myocardial fibrosis to regulate lots of cardiovascular diseases, such as atherosclerosis, congestive heart failure and systemic hypertension. STIM1 is closely related to cardiovascular diseases through calcium signal. The research progress of STIM1 in cardiovascular diseases is mainly discussed in this article.