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To investigate the relationship between intracellular free Ca2+ concentration ([Ca2+]i)and calcium-activated chloride (Clca) channels of pulmonary artery smooth muscle cells (PASMCs) in rats under acute and chronic hypoxic conditions, acute hypoxia-induced contraction was observed in rat pulmonary artery by using routine blood vascular perfusion in vitro. The fluorescence Ca2+indicator Fura-2/AM was used to observe [Ca2+]i of rat PASMCs under normal and chronic hypoxic condition. The effect of Clca channels on PASMCs proliferation was assessed by MTT assay.The Clca channel blockersniflumic acid (NFA) and indaryloxyacetic acid (IAA-94) exerted inhibitory effects on acute hypoxia-evoked contractions in the pulmonary artery. Under chronic hypoxic condition, [Ca2+ ]i was increased. Under normoxic condition, [Ca2+]i was (123.63±18.98) nmol/L, and in hypoxic condition, [Ca2+]i was (281. 75±16.48) nmol/L (P＜0.01). Under normoxic condition, [Ca2+]i showed no significant change and no effect on Clca channels was observed (P＞0. 05). Chronic hypoxia increased [Ca2+]i which opened Clca channels. The NFA and IAA-94blocked the channels and decreased [Ca2+]i from (281. 75±16.48) nmol/L to (117.66±15.36)nmol/L (P＜0.01). MTT assay showed that under chronic hypoxic condition NFA and IAA-94 decreased the value of absorbency (A value) from 0. 459±0. 058 to 0. 224±0. 025 (P＜0.01).Hypoxia increased [Ca2+]i which opened Clca channels and had a positive-feedback in [Ca2+]i. Thismay play an important role in hypoxic pulmonary hypertension. Under chronic hypoxic condition,Clca channel may play a part in the regulation of proliferation of PASMCs.
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Aim To investigate change in Cl- channels of hypertensive rats aortic smooth muscle cells. Methods 2 kidney-2 clip renovascular hypertensive rats(RVHR) model was established. In thoracic aorta smooth muscles from the hypertensive rats 1～12 weeks after operation,the changes of tension of aortic rings were recorded in vitro. Effects of Cl- channel blookers,DIDS(4,4-diisothiocyanato-stilbene-2,2'disulphonate)and NPPB[5-nitro-2-(3-phenylpropy-lamino) benzonic acid], in different concentration on contractile response of hypertensive rats aorta smooth muscle induced by 10 ?mol?L -1 phenylephrine were observed.Results The difference of inhibitory effects of 300 ?mol?L -1 DIDS and 100 ?mol?L -1 NPPB on Phe-induced contractile response between RVHR and sham-operated rats was not evident.Inhibitory effects of 300 ?mol?L -1 DIDS and 100 ?mol?L -1 NPPB on contractile response of hypertensive rats aorta smooth muscle induced by 10 ?mol?L -1 phenylephrine were lower than those of sham-operated rats in 8 weeks and 12 weeks after operation. With extension of time after operation and gradual increase of blood pressure in RVHR,inhibitory effects of DIDS and NPPB on Phe-induced contractile response gradually reduced.Conclusion Action of DIDS-sensitive and NPPB-sensitive Cl- channels in hypertensive rats aortic vascular smooth muscle cells changes. DIDS-sensitive and NPPB-sensitive Cl- channels play an important role in development and maintenance of hypertension.
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AIM: To investigate the relationship between chloride channels and the Ca 2+influx induced by adrendine(Adr). METHODS: The effects of drugs on Adr-induced Ca 2+influx were investigated with Fura-2 fluorescence technique. RESULTS: Adr-induced Ca 2+influx was inhibited by nifedipine,SK&F96365,NFA and furosemide in a concentration manner respectively; Ca 2+influx could be further inhibited by NFA or furosemide after the maximal inhibition by SK&F96365;SK&F96365 also could further inhibit the Ca 2+influx which had been inhibited by NFA or furosemide. Genistein and vanadate could reduce or increase the Ca 2+influx respectively. CONCLUSION: Ca 2+influx induced by Adr is related to VDC and ROC, and chloride channels involves in the processes.The levels of tyrosine phosphoralation affect the Ca 2+influx.
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Subject(s)
Animals , Chloride Channels/metabolism , Chloride Channels/biosynthesis , Choroid Plexus/metabolism , Choroid Plexus/cytology , Epithelial Cells/metabolismABSTRACT
AIM To investigate the roles of Cl- channels in Ca2+ influx induced by activaion of al- adrenoceptor subtypes in transfected-CHO cells. METHODS The effects of drugs on ?1A、?1B and ?1D- AR-induced Ca2+ influx were investigated with Fura2 fluorescence technique. RESULTS The ?1A-AR- induced Ca2+ influx was inhibited by furosemide(2 .5 ~ 10 M?mol?L- 1 )and SK&F96365(5- 15 ?mol?L- 1 ) in a concentration- dependent manner respectively; The ?1B-AR-induced Ca2+ influx could also be inhibit inhibited by NFA(2. 5 ~ 10 ?mol? L-1 ), whereas the alD AR-induced Ca2+ influx was only suppressed by NFA. In ?1B-CHO cells, Adr-triggered Ca2+ influx could be further inhibited by NFA or furosemide after the maximal inhibition by SK&F96365;SK&F96365 could further inhibit Ca2+ influx which had been inhibited by NFA or furosemide. In ?1A-CHO cells, Adr-triggered Ca2+ influx could be further inhibited by SK&F96365 after had been inhibited by furosemide; furosemide could not further inhibite Ca2+ influx which had been inhibited by S&F96365. CONCLUSION There are different characteristics of CI- channels related to ?1A、 ?1B and ?1D-AR-induced Ca2+ influx.
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AIM To examine the role of Cl - channels in endothelin 1 (ET 1) induced proliferation of vascular smooth muscle cells (VSMCs). METHODS Through cell counting and 3H TdR incorporation, together with [Ca 2+ ] i measurement by fura 2/AM fluorescence, we studied the effects of Cl - channel blockers on proliferation of VSMCs induced by ET 1. RESULTS Cl - channel blocker, DIDS, inhibited 10 nmol?L -1 ET 1 induced proliferation of VSMCs in a concentration dependent manner, however,other Cl - channel blockers such as IAA 94, NPPB, SITS, DPC and furosemide, all failed to inhibit ET 1 induced proliferation of VSMCs. DIDS reduced 10 nmol?L -1 ET 1-induced sustained [Ca 2+ ] i elevation but not Ca 2+ release from internal stores; Pretreatment of cells with 1 ?mol?L -1 nifedipine abolished the inhibitory effect of 3 ?mol?L -1 DIDS on proliferation of VSMCs and [Ca 2+ ] i elevation evoked by 10 nmol?L -1 ET 1 , while after cells were pretreated with 10 ?mol?L -1 SK&F96365, the same concentration of DIDS could also inhibit the aforecited effects of ET 1;3 ?mol?L -1 DIDS had no effect on 30 mmol?L -1 KCl induced elevation of [Ca 2+ ] i. CONCLUSION DIDS inhibited Ca 2+ influx and VSMCs proliferation induced by ET 1 through blockade of DIDS sensitive Cl - channels, and these channels may play important roles in modulating Ca 2+ influx and VSMCs proliferation induced by ET 1.