Effects of levcromakalim on pulmonary arterial endothelial cells and smooth muscle cells exposed to hypoxia

AIM:To explore the effects of levcromakalim(Lev) on pulmonary arterial endothelial cells (PAEC) and smooth muscle cells (PASMC) exposed to hypoxia and the mechanisms involved.METHODS:The effects of Lev on [Ca²⁺]_i, and expression of PKC_α, eNOS, iNOS and PDGF-B mRNA and protein levels were observed. The nitrite (NO₂^-) and entothelin-1(ET-1) concentrations in supernatant in cultured PAEC and PASMC were measured. The proliferation and apoptosis of PASMC was also detected.RESULTS:When PASMC were exposed to hypoxia, Lev reduced concentration of ET-1 in cultured cell supernatant, lowed the expression of PKC_α, iNOS and PDGF-B both at mRNA and protein levels, decreased [Ca²⁺]_i concentration, increased proliferation and promoted the apoptosis in PASMC. However, in the presence of Lev, the [Ca²⁺]_i concentration was not changed in the hypoxic PAEC. The NO₂^- concentration in cultured cell supernant and expression of eNOS at mRNA and protein levels in hypoxic PASMC and PAEC were also unchanged. The downregulated ET-1 activity in PASMC and PAEC and proliferation in PASMC involved in the inhibition of PKC_α signaling pathway.CONCLUSIONS:Lev reduce some disadvatage effect of hypoxia on PASMC and PAEC. The mechanism of Lev action may partly involve in the downregulation of PKC_α signaling functions.     

Role of K+ channels in attenuation of pulmonary vasoreactivity following chronic hypobaric hypoxia in rats

AIM and METHODS: To determine the role of different K⁺-channels in attenuation of vasoreactivity of intrapulminary artery rings induced by chronic hypoxia. RESULTS: ①Acute hypoxia-induced pulmonary vasoconstriction (HPV) could be significantly attenuated by chronic hypobaric hypoxia for 15 days and for 30 days. ②HPV could be significantly potentiated by ATP-sensitive K⁺-channel (K_ATP) blocker or Ca²⁺-activated K⁺-channel (K_Ca) blocker, and the potentiated scope in chronic hypoxic group was much higher than that observed in control group. ③Delayed rectifier K⁺-channel (K_DR) blocker showed no effect on HPV in both control group and chronic hypoxic group. CONCLUSION: Both K_ATP and K_Ca play an important modulating role in HPV and its potentiation may be a critical mechanism for the attenuated vasoreactivity to acute hypoxia following chronic hypobaric hypoxia.     

Role of K+ channels in hypoxic pulmonary vasoconstriction in normal and chronic hypoxic rats

AIM:To investigate the role of K⁺ channels in the decreased hypoxic pulmonary vasoconstriction(HPV) in chronic hypoxic rats. METHODS:Blockers of three kinds of K⁺ channels, 4-AP(voltage dependent K⁺ channel blocker), TEA(Ca²⁺ activated K⁺ channel blocker), GLIB(ATP sensitive K⁺ channel blocker) were used in isolated perfused rat lungs to detect the role of K⁺ channels in HPV. RESULTS:In normal rats, 4-AP and TEA, but not GLIB, both elicited a significant increase in pulmonary artery baseline pressure, and also potentiated the acute hypoxic pulmonary vasoconstriction. In chronic hypoxic rats, the HPV is significantly decreased, while 4-AP, TEA, GLIB all elicited a significant but smaller increase in pulmonary artery baseline pressure. Additionally, all these three blockers potentiated the HPV stronger in chronic hypoxic rats than in control rats. CONCLUSION:The opening of Kv, K_Ca, K_ATP might modulate the hypoxic pulmonary vasoconstriction in isolated rat lungs, and the increase in this modulation by potassium channel in chronic hypoxic rats might play a role in its decrease in HPV.     

Role of potassium channels in the regulation of intracellular free Ca2+ concentration of pulmonary artery smooth muscle cells in rats

AIM: To investigate the role of potassium channels in the regulation of intracellular free calcium concentration ( [Ca²⁺]_i) of pulmonary artery smooth muscle cells (PASMCs) in rats. METHODS: The fluorescence Ca²⁺ indicator Fura-2/AM was used to observe [Ca²⁺]_i of rat PASMCs in normal and chronic hypoxic condition. The influences of potassium channels on PASMCs proliferation were assessed by MTT assay. RESULTS: 1. In normoxic condition, [Ca²⁺]_i was (156.91±8.60) nmol/L, and in hypoxic condition, [Ca²⁺]_i was (294.01±16.81) nmol/L. 2. In normoxic condition, the voltage-dependent K⁺-channel antagonist 4-aminopyridine (4AP), but not the Ca²⁺-activated K⁺-channel antagonist tetraethylammonium (TEA) and the ATP-sensitive K⁺-channel antagonist glibenclamide (Glib) increased [Ca²⁺]_i. 3. In hypoxic condition, 4AP and TEA caused the rise in [Ca²⁺]_i , but Glib had no effect on [Ca²⁺]_i. 4. MTT assay showed that 4AP increased the value of absorbing light degree (A value) in normoxic and hypoxic condition (0.582±0.062,0.873±0.043,respectively, P＜0.01), TEA increased A value only in hypoxic condition, and Glib had no effect on the proliferation of PASMCs. CONCLUSIONS: K_V plays an important role in the regulation of [Ca²⁺]_i and proliferation of PASMCs. K_Ca serves as distinct responsive roles in the regulation of proliferation of PASMCs in hypoxic condition. K_ATP has no effect on [Ca²⁺]_i and proliferation of PASMCs in normoxic and hypoxic conditions.     

Inhibitory effect of Salidroside on the proliferation of rabbit pulmonary artery smooth muscle cells under hypoxia

AIM: To investigate the effect of Salidroside on the proliferation, DNA synthesis, intracellular Ca²⁺ content of rabbit PASMC (pulmonary artery smooth muscle cells) under hypoxia. METHODS: Techniques of cell culture, MTT test, [³H][³H][³H]-TdR incorporation, fluo-3 and confocal laser scanning microscopy were used. RESULTS: The A value of MTT and [³H][³H]-TdR incorporation of PASMC increased significantly by 62% (P＜0.05) and 138% (P＜0.01) after 24 h hypoxia. Salidroside (32×10^-5 mol/L) inhibited the action of hypoxia on the proliferation of PASMC, the A value of MTT and [³H][³H]-TdR incorporation declined significantly by 29% (P＜0.05) and 37% (P＜0.01) compared with hypoxia group. A calcium channel blocker, verapamil could also inhibit the accelerative effect of hypoxia on the proliferation of PASMC. The intracelluler Ca²⁺ content of PASMC raised markedly under hypoxia, but the effect of hypoxia on the intracelluler Ca²⁺ content could be inhibited by Salidroside. CONCLUSION: Salidroside inhibited the proliferation, DNA synthesis of PASMC induced by hypoxia. The inhibitory action of Salidroside on the increase in intracellular Ca²⁺ concentration under hypoxia might be one of the mechenisms.     

Effect of BQ123 on the voltage-gated K+ current of pulmonary artery smooth muscle cells of rats exposed to chronic hypoxia

AIM:To study the effect of BQ123 on voltage-gated K+ current in pulmonary artery smooth muscle cells (PASMCs) from chronic hypoxic rats. METHODS:Twelve age and body weight matched Wistar rats were randomly divided into control and chronic hypoxic group. Single PASMCs were obtained with acute enzyme (collagnaseⅠ plus papain) dispersing method. Using the whole cell patch-clamp technique in freshly isolated PASMCs from normorxic and hypoxic rats, the effects of ET-1 and BQ123, a selective ETA receptor antagonist, on voltage-gated K+ current were recorded. RESULTS:(1) ET-1 (10-8 mol·L-1) caused inhibition of K+ current in PASMCs from normoxic and hypoxic rats. The effect of ET-1 on K+ current in PASMCs from hypoxic rats was greater than that from normoxic rats ［+50 mV, percent inhibition were (71.04±6.58)% and (60.21±5.32)%, respectively, P<0.01, n=6］. (2) In normoxic PASMCs, neither BQ123 alone produced influence on the IKV (P>0.05, n=5), nor ETA receptor blockade had change of ET-1 mediated IKV inhibition. (3) In chronic hypoxic PASMCs, BQ123 significantly reduced the effect of ET-1 mediated IKV inhibition, from (28.49±6.69) pA/pF to (74.19±9.74) pA/pF at +50 mV (P<0.01, n=6). CONCLUSION:In normoxic condition, the effect of ET-1 on IKV of PASMCs is not mediated by BQ123, a selective ETA receptor antagonist. During exposure to chronic hypoxia, the inhibition of ET-1 on IKV of PASMCs is partly mediated by BQ123, namely, ETA receptor mediates the effect of ET-1 on IKV of chronic hypoxic PASMCs.     

Effect of diazoxide on change of H2O2 in rat pulmonary artery smooth muscle cells and proliferation of hypoxic rat pulmonary artery smooth muscle cells

AIM: To investigate the contribution of diazoxide,an opener of mitochondrial ATP-sensitive K+ channel (MitoK_ATP),and mitochondrial membrane potential (ΔΨm) to change of H₂O₂ in rat pulmonary artery smooth muscle cells (PASMCs) and to unbalance between cell proliferation and apoptosis of PASMCs induced by hypoxia.METHODS: The rat PASMCs were isolated from fresh normal lung tissues and cultured,which were divided into 6 groups,as follows: ① control group;② diazoxide group;③ 5-HD group;④chronic hypoxia group;⑤ chronic hypoxia+diazoxide group;⑥ chronic hypoxia +5-HD group.The relative change in mitochondrial potential was detected with rhodamine fluorescence (R-123) technique.The level of H₂O₂ in rat PASMCs was detected with chemiluminescence method.The proliferation of rat PASMCs was examined by cell cycle analysis and MTT colorimetric assay.RESULTS: After exposed to diazoxide for 24 h,the intensity of R-123 fluorescence,the level of H₂O₂ and the A value in normoxic rat PASMCs were significantly increased,and the apoptosis of rat PASMCs was significantly decreased as compared with control group (P<0.05).However,there were no significant changes in these tests after the rat PASMCs had been exposed to 5-HD for 24 h.Chronic hypoxia or chronic hypoxia+diazoxide markedly increased the intensity of R-123 fluorescence,the level of H₂O₂ and the A value in rat PASMCs,and also markedly decreased the apoptosis of rat PASMCs as compared with control group (P<0.05),and these changes were more significant in chronic hypoxia +diazoxide group than those in chronic hypoxia group (P<0.05).5-HD partly weakened the effect of hypoxia on the intensity of R-123 fluorescence,the level of H₂O₂,the A value and the apoptosis of rat PASMCs (P<0.05).Significant and positive correlations were found between the intracellular H₂O₂ and the R-123 fluorescence or the A value.Significant and negative correlation was found between the intracellular H₂O₂ and the apoptosis of rat PASMCs.CONCLUSION: The results suggest that the opening of MitoK_ATP followed by a depolarization of ΔΨm can contribute to the increase in the level of H₂O₂ in rat PASMCs and to the proliferation of rat PASMCs induced by hypoxia.This might be a mechanism of the development of hypoxic pulmonary hypertension.     

Effects of docosahexaenoic acid on large-conductance calcium-activated potassium channels in rat pulmonary artery smooth muscle cells

AIM：To investigate the effects of docosahexaenoic acid (DHA) on large-conductance calcium-activated potassium channels (BKCa) in rat pulmonary artery smooth muscle cells (PASMCs)．METHODS：BKCa currents in individual PASMCs were recorded by patch-clamp technique in whole-cell configuration．Calcium sparks in PASMCs caused by DHA were recorded by confocal microscopy. RESULTS：DHA activated BKCa . BKCa current densities were (30.5±6.5)pA/pF,(59.4±5.8)pA/pF, (87.2±4.3)pA/pF and (117.3±7.1) pA/pF (P<0.01) with the addition of DHA at concentrations of 0, 0.1, 1 and 10 μmol/L, respectively. Hypoxia inhibited BKCa currents in PASMCs, but this inhibition was reversed by DHA (10 μmol/L). DHA (10 μmol/L) induced an increase in ［Ca2+］i with a maximal increase rate of (71.9±4.1)%. CONCLUSION：DHA activates BKCa in rat PASMCs, leading to the vasodilation of pulmonary arteries.     

Chronic hypoxia altered the expression of ET-1 mRNA in response to acute hypoxia in pulmonary artery endothelial cells

AIM:To investigate the expression of ET-1 mRNA in porcine pulmonary artery endothelial cells cultured in normoxic and chronic hypoxic conditions, and their different responses to acute hypoxia were also evaluated.METHODS:Insituhybridization and image -analysis system were used. RESULTS:Acute hypoxia enhanced the expression of ET-1 mRNA in both normoxic and chronic hypoxic group. The increment was more significant in the latter group.CONCLUSION:Chronic hypoxia increased the expression of ET-1 mRNA in response to acute hypoxia in porcine pulmonary artery endothelial cells.     

Expression of voltage-gated potassium channel gene of pulmonary artery smooth muscle cells in COPD merge chronic hypoxic patients

AIM: To study the change of expressions of Kv1.2, Kv1.3, Kv1.5, Kv2.1, Kv3.1 genes in pulmonary artery smooth muscle cells (PASMCs) on COPD merge chronic hypoxic patients. METHODS: Human lung tissue was collected from surgical patients. RT-PCR technique was used to study the expression of Kv1.2, Kv1.3, Kv1.5, Kv2.1 and Kv3.1 genes. PASMCs were divided into two groups: ① PASMCs from normal human pulmonary artery, pure COPD patients and COPD merger chronic hypoxic patients pulmonary artery； ② Cultured PASMCs exposed to continual chronic hypoxia or normoxia. RESULTS: ① The expression of Kv1.2, Kv1.3, Kv1.5, Kv2.1, Kv3.1 encoding genes were found in human PASMCs exposed to either normixa or chronic hypoxia. ② The expression of Kv1.2, Kv1.5, Kv2.1 genes in PASMCs exposed to chronic hypoxia were significantly decreased compared with control groups (P<0.05). ③ The expression of Kv1.3, Kv3.1 genes in PASMCs exposed to chronic hypoxia showed no significant change compared with control groups (P>0.05). ④ The expression of Kv1.2, Kv1.5, Kv2.1, Kv3.1 genes in pure COPD patients were significantly increased compared with control groups (P<0.05). CONCLUSIONS: ①The results suggested that Kv1.2, Kv1.5, Kv2.1 genes may be oxygen sensitive gene. Their expressions are affected by chronic hypoxia, which probably play an important role in human pulmonary artery hypertension. ② Kv1.3, Kv3.1 genes may not be oxygen sensitive gene and their expression are not affected by chronic hypoxia, which might play a secondary role in human pulmonary artery hypertension.     

Role of prostaglandins,nitric oxide and potassium channel in the blunting of hypoxic pulmonary vasoconstriction in the high altitude adaptive animal

AIM: To investigate the possible role of prostaglandin, NO and potassium channel in the adaptive blunting of hypoxic pulmonary vasoconstriction (HPV) in high altitude animal (pika). METHODS: The effect of L-NAME, indomethacin and 4-AP on the response of isolated lung strips of pika and Wistar rats instead of pulmonary artery to acute hypoxia were studied. RESULTS: (1) After inhibition of prostaglandins by indomethacin, the percentage increase in hypoxic constriction in lung tissue strip of pikas was greater than that in Wistar rats , P＜0.05; (2) After inhibition of NO synthesis by L-NAME, the percentage increase in hypoxic constriction in lung tissue strip of pikas was greater than that in Wistar rats , P＜0.05; (3) After administration of 4-AP, there was no significant difference in the percentage decrease in hypoxic constriction of lung tissue strip between pika and Wistar rat. CONCLUSIONS: (1) Prostaglandins and NO might modulate HPV in either rat of pika; the closure of Voltage-gated K⁺ channels might mediate HPV in either rat or pika. (2) Prostaglandins and NO might play an important role in the blunting of HPV in pika, Voltage-gated K⁺ channels may play a minor role in the blunting of hypoxic pulmonary vasoconstriction in pika.     

Influences of chronic hypoxia on the gene expression of Kv1.3,Kv2.1 and Kv3.1 induced by acute hypoxia in PASMC of rats

AIM and METHODS: Total RNA was extracted from 6th rat subcultured pulmonary artery smooth muscle cells(PASMC) exposed to continual chronic hypoxia or normoxia and the effects of chronic hypoxia on the changes of Kv1.3,Kv2.1,Kv3.1 mRNA in cultured PASMC induced by acute hypoxia were studied by semiquantitative RT-PCR in vitro. RESULTS:①Kv1.3,Kv2.1,Kv3.1 genes were found to be expressed in PASMC of rats exposed either to hypoxia or normxia.②The expression of Kv2.1 and Kv3.1 in 6th subcultured of PASMC in normaxia group could be upregulated by exposure to acute hypoxia,the levels of Kv2.1 and Kv3.1 mRNA were significantly increased from 0.646±0.092, 0.782±0.104 to 1.059±0.134, 0.985±0.116,respectively (P<0.01,n=5). ③PASMC cultured continuously in chronic hypoxia for 6 subcultures and then exposed to normoxia for 12 h,thereafter the expression of Kv2.1 and Kv3.1 were downregulated by acute hypoxia for 6 hours.The level of Kv2.1 mRNA was significantly decreased from 1.008±0.117 to 0.649±0.097 (P<0.01,n=5). CONCLUSION:Kv2.1,Kv3.1 genes might be oxygen sensitive genes.Chronic hypoxia might change the response of these Kv genes of PASMC to acute hypoxia and down-regulate its expression,which might probably decrease the role of Kv in HPV.     

Studies of potassium channel in pulmonary artery smooth muscle cells of pulmonary hypertension rats

AIM：In this work,we investigated the difference of membrane capacitance,membrane current,current density and I-V curves between smooth muscle cells isolated from pulmonary hypertension rat (PHR) or normotensive rat (NTR) pulmonary arteries.METHODS：Thirty young male Sprague-Dawley rats,aged 8-9 weeks,were used.Body weight was (200±20)g at the start of experiments.These rats were placed into a normobaric chamber for 6 h·day-1,6 day·week-1 for 4 weeks.Hypoxic exposure was accomplished by ventilation with room air and N2 resulting in a constant O2 concentration of (10±0.5)%.Whole cell recordings were made from smooth muscle cells freshly isolated from pulmonary arteries derived from PHR or NTR.RESULTS：The membrane capacitance of pulmonary hypertension rats was larger than that in SD rats;but membrane current and current density were lower than those in SD rats (P<0.05).The I-V curves of pulmonary hypertension rat were downward shift compared with that in SD rat.Iptakalim hydrochloride 10 μmol·L-1 significantly increased potassium currents.CONCLUSIONS：Membrane capacitance,membrane current,membrane potential are decreased,I-V curves was shift downward,compared with NTR.Iptakalim hydrochloride significantly increased NTR and PHR potassium currents.     

Effects of hypoxia-inducible factor-1 signal pathway on proliferation in hypoxic pulmonary artery smooth muscle cells

AIM: To investigate the effect of hypoxia on the proliferation and apoptosis of pulmonary artery smooth muscle cells (PASMC); and to evaluate the role of hypoxia-inducible factor-1α(HIF-1α), iNOS, P-ERK1/2 protein expression in hypoxic pulmonary hypertension (HPH) pathogenesis.METHODS: Cultured rat PASMC were divided into normoxic group; hypoxic group; hypoxia+ADM(adrenomedulin) group, hypoxia+L-NAME(iNOS inhibitor) group; hypoxia+PD98059 group. Proliferation was investigated by MTT and PCNA. Apoptosis was examined by flow-cytometry. Westen blotting was used to measure protein expression of HIF-1α, P-ERK1/2 and iNOS. RESULTS: (1) A value of 24 h-hypoxia was significantly higher than that in the normoxic group (P<0.01). In the hypoxia+PD98059 group, ADM was significantly lower than that in hypoxia group, whereas A value of the hypoxia+L-NAME was significantly higher than that in hypoxic group and normoxic group (P<0.01). (2) PCNA was positive in PASMC after 24 h hypoxia (P<0.01). PD98059, ADM inhibited the expression of PCNA significantly (P<0.01), whereas L-NAME increased the expression of PCNA significantly (P<0.01). (3) Apoptosis index was not significantly difference among the different groups (P>0.05). (4) HIF-1α, iNOS and P-ERK1/2 expression was poorly positive in normoxic group, positive after hypoxia for 4h (P<0.01), reaching its peak at 8 h hypoxia (P<0.01), HIF-1α, P-ERK1/2 expression declined after 24 h hypoxia. L-NAME promoted the expression of HIF-1α, PD98059 inhibited the expression of HIF-1α, iNOS and P-ERK1/2 partly. ADM inhibited the expression of HIF-1α partly, promoted the expression of iNOS. CONCLUSION: (1) Hypoxia stimulates the proliferation of PASMC, and has no obvious effects on the apoptosis of PASMC. (2) HIF-1 plays an importent role in the proliferation of hypoxic PASMC.     

Expression of bFGF mRNA in pulmonary artery of rat with chronic hypoxia and its effect on tension of rat pulmonary artery in vitro

AIM: To explore the role of basic-fibroblast growth factor (bFGF) in the development of pulmonary hypertension induced by hypoxia. METHODS: 1) The pulmonary arteries of SD rats with hypoxia for one and two weeks were isolated, from which the total RNA were extracted by acid guanidinium thiocyanate-phenol-chlorform .Then the levels of mRNA were measured by RT-PCR. 2) About 3mm-long arterial rings cut from SD rat pulmonary arterial stem were suspended between stainless steelhooks in chamber with warmed (37℃) Kreb's solution. Different concentrations of bFGF were added in a cumulative fashion into the chamber where the rings were suspended. The cumulative concentration response curve was obtained. RESULTS: 1)The levels of bFGF mRNA in pulmonary artery of rats with hypoxia were increased significantly compared with those that without hypoxia (2578±384 counts·min^-1 (control) vs 5303±756 (hypoxia) for 1 week and 4054±547 (hypoxia) for 2 weeks, P all ＜0.05). 2) bFGF at concentrations ranged from 5.56×10^-10~2.78×10^-7mol/L caused dose-dependent contraction of vessel rings of rat pulmonary artery (r=0.695,P＜0.05), with EC₅₀ being 2.62×10^-7mol/L. CONCLUSION: bFGF may play an important role in the hypoxic pulmonary hypertension.     

Effect of chronic hypoxia on [Ca2+]iin pulmonary artery endothelial cells and smooth muscle cells under acute hypoxia

AIM AND METHODS: Using Ca²⁺-sensitive fluorescent probe Fura-2,we measured the changes of [Ca²⁺]_iin cultured rat pulmonary artery endothelial cells (PAEC) and porcine pulmonary artery smooth muscle cells (PASMC) from normoxic (NC group) or chronic hypoxic group (CH group) when they were exposed to acute hypoxia. RESULTS: The increase in [Ca²⁺]_iin 6th passage of PASMC caused by acute hypoxia in CH group was significantly lower than that in the same passage of NC group (P<0.05).On the contrary, in PAEC, the acute hypoxia induced increase in _i, which was significantly higher in 5th passage of CH group than that in NC group (P<0.05). CONCLUSION: The decrease of the elevation of [Ca²⁺]_icaused by acute hypoxia in PASMC of CH group indicated that it functioned to lower the constrictive response to hypoxia.The intensive increase in [Ca²⁺]_icaused by acute hypoxia in PAEC of CH group might lead to more relaxing factors derived from PAEC,which results in a decrease in HPV.     

Roles of the Kv1.2, Kv1.5, Kv2.1 potassium channels in hypoxia pulmonary vasoconstriction

AIM: To determine the role of Kv1.2, Kv1.5, Kv2.1 in the hypoxia pulmonary vasoconstriction (HPV). METHODS: Male Wistar rats were divided into two groups: normoxic group and hypoxic group. The single smooth muscle cell was obtained from pulmonary artery of Wistar rats with acute enzymatic digestion method. The conventional whole-cell patch clamp technique was used to record the resting membrane potential (Em) and the potassium currents of voltage-gated potassium channel (IKv) in rat pulmonary arterial smooth muscle cells (PASMC). Intracellular application of Kv1.2/Kv1.5/Kv2.1 antibodies (1∶125) was conducted through the whole-cell patch clamp system. RESULTS: ① Em of PASMC was depolarized after 24 h hypoxia compared with that of control cells . IKv of PASMC was decreased after 24 h hypoxia, . ② The mixture of Kv1.2/Kv1.5/Kv2.1 antibodies depolarized Em and inhibited IKv in PASMC from normoxic rat, whereas the mixture of Kir2.1/Kir2.3/Kir4.1 antibodies had no effects on them. ③ The mixture of Kv1.2/Kv1.5/Kv2.1 antibodies and the mixture of Kir2.1/Kir2.3/Kir4.1 antibodies had no effects on IKv and Em from rats hypoxic for 24 h. CONCLUSION: Kv1.2, Kv1.5, Kv2.1 might be oxygen sensitive potassium channels which mediated HPV.     

Role of cyclic nucleotides in the acute hypoxic responses of hypoxic subcultured porcine pulmonary arterial smooth muscle and endothelial cells

AIM: To detect the role of cyclic nucleotides in the alleviation of hypoxic pulmonary vasoconstriction (HPV) in chronic hypoxic animals. METHODS: The intracellular cAMP and cGMP of the cultured porcine pulmonary arterial smooth muscle cells (PASMC) and endothelial cells (PAEC) were assayed by RIA. The length of single PASMC during acute hypoxia was measured by imaging analysis system. RESULTS: The basal levels of cAMP and cGMP in PASMC and cGMP in PAEC of Chronic hypoxic groups decreased remarkably compared with normoxic groups (P＜0.01). Under acute hypoxia, the contents of cAMP and cGMP in PASMC of chronic hypoxic groups increased significantly (P＜0.01). Meanwhile, the percentage of PASMC with weak constrictive response in chronic hypoxic group was higher than that of control group. CONCLUSION:It's suggested that the changes of cAMP and cGMP in chronic hypoxic PASMC and PAEC might contribute to the increase in the basic tension of pulmonary artery and the alleviation of HPV in chronic hypoxic animals.