Objective: To study the effect and the mechanism of acute hypoxia on Ca2+-ATPase inhibitor, cyclopiazonic acid (CPA) induced intracellular calcium cation enhancement in rat distal pulmonary venous smooth muscle cells (PVSMC) .
Methods: The PVSMC were isolated from 6 male SD rats and the cells were cultured for further experiment. Enhancing effects of CPA, acute hypoxia (4% O2) on [Ca2+]i in distal PVSMC and the interventional effects of 2 store-operated Ca2+ channels (SOCC) inhibitors, NiCl2 and SKF96365 on [Ca2+]i in distal PVSMC were tested by lfuorescence microscope and intracellular [Ca2+] examining system.
Results: When PVSMC were perfused with Ca2+-free Krebs solution containing 5 μmol/L nifedipine, 10 μmol/L CPA caused a slight elevation of [Ca2+]i, and acute hypoxia obviously enhanced the [Ca2+]i in PVSMC. When restoration of extracellular [Ca2+] to 2.5 mmol/L, 10 μmol/L CPA caused signiifcant elevation of [Ca2+]i, and acute hypoxia obviously enhanced [Ca2+]i induced by CPA in PVSMC. The SOCC inhibitors, NiCl2 (500 μmol/L) and SKF96365 (50 μmol/L) distinctively attenuated the elevation of [Ca2+]i by hypoxia and CPA. However, NiCl2 and SKF96365 had no effect on high potassium (60 mmol/L KCl Krebs solution) induced elevation of [Ca2+]i in distal PVSMC.
Conclusion: Acute hypoxia enhanced the elevation of [Ca2+]i induced by CPA; such effect could be selectively blocked by SOCC inhibitor which indicated that acute hypoxia could enhance the activity of SOCC in rat distal PVSMC.

Objective To study the effect of SKF96365 and NiCl2 on cyclopiazonic acid (CPA) induced intracellular calcium cation concentration ([Ca2+ ]i ) change in rat distal pulmonary arterial smooth muscle cells (PASMC) .Methods The rat distal PASMC were isolated and cultured .The effects of CPA ,SKF96365 and NiCl2 on [Ca2+ ]i in PASMC were tested by fluorescence microscope and InCyte [Ca2+ ]i measurement system .Results PASMC were incubated with Ca2+‐free Krebs solution containing 5μmol/L nifedipine ,10 μmol/L CPA caused a small transient increase in [Ca2+ ]i ;after restoration of extracellular Ca2+ to 2 .5 mmol/L ,10 μmol/L CPA caused marked increases in [Ca2+ ]i in PASMC incubated with Krebs solution containing 5 μmol/L nife‐dipine .Both 50 μmol/L SKF96365 and 500 μmol/L NiCl2 distinctly attenuated the increases in [Ca2+ ]i caused by 10 μmol/L CPA in PASMC .However ,neither 50 μmol/L SKF96365 nor 500 μmol/L NiCl2 affected the increases in [Ca2+ ]i caused by 60 mmol/L KCl in PASMC .Conclusion CPA induced increases in [Ca2+ ]i may related to Ca2+ release from sarcoplasmic reticulum and the in‐flux of Ca2+ through store‐operated Ca2+ channels (SOCC) in rat distal PASMC .Both SKF96365 and NiCl2 could selectively block SOCC and attenuated the influx of Ca2+ through SOCC in PASMC .

AIM: The effect of urotensin II (U-II) on proliferation of cultured pulmonary arterial smooth muscle cells (PASMCs) of rabbits and its mechanism are investigated. METHODS: PASMCs were isolated using explant technique. RPASMCs were incubated in serum-free medium with different concentrations of nicardipine, calcimodulin antagonist W 7, PKC inhibitor H 7 or MAPK inhibitor (PD 98059 ), with or without U-II. RPASMC proliferation was examined by MTT [3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay and by the increase in [ 3H]-thymidine incorporation into DNA. RESULTS: U-II (10 -9 mol/L-10 -7 mol/L) increased A value of PASMCs by MTT assay and [ 3H]-thymidine incorporation in PASMCs in a dose-dependent manner. U-II induced a maximal effect at a concentration of 10 -7 mol/L. A value and [ 3H]-thymidine incorporation rose 42 9% and 68 5% ( P

Objective To determine whether store-operated Ca2+ entry (SOCE) is involved in chronic hypoxia-induced alteration of intracellular Ca2 + concentration ([Ca2+] i) and proliferation in pulmonary arterial smooth muscle cells (PASMC).Methods Rat PASMCs were cultured and treated in normoxia (21％O2) or hypoxia (4％ O2) condition.The proliferation of PASMC was detected by cell counting kit-8 (CCK-8) assay.[Ca2 +] i,SOCE and the effects of store-operated Ca2 + channel (SOCC) inhibitors,SKF96365 and NiCl2,on SOCE in hypoxic PASMCs were tested by InCyte [Ca2 +] i measurement system.Results Hypoxia for 24-60 h augmented PASMC proliferation (1.12 ± 0.09 vs 0.71 ± 0.05,P ＜ 0.05) and [Ca2 +] i [(214.8 ± 20.4) nmol/L vs (115.2 ± 13.2) nmol/L,P ＜ 0.05] in a time-dependent manner with the maximum effect at 60 h.Perfusion of Ca2+-free Krebs solution containing nifedipine (5 μ mol/L),cyclopiazonic acid (CPA,10 μmol/L) in PASMCs caused a small transient increase of [Ca2+]i with peak [Ca2+]i (113.3 ± 49.3) nmol/L.Chronic hypoxia (4％ O2,60 h) enhanced [Ca2+]i level with peak value of (193.2 ± 22.7) nmol/L (P ＜ 0.05) in PASMC.After restoration of extracellular Ca2+,CPA caused marked increase of [Ca2+]i with peak value of (328.0 ± 56.7) nmol/L.Chronic hypoxia strengthened CPA-induced increase of [Ca2 +] i with peak value of (526.0 ± 33.7) nmol/L (P ＜ 0.05) in PASMCs.Either SKF96365 50 μmol/L or NiCl2 500 μmol/L distinctly attenuated CPA-induced enhancement of [Ca2 +] i,the peak value of which dropped from (526.0 ± 33.7) nmol/L to (170.4 ± 26.4) nmol/L (P＜0.05) or (177.4±45.9) nmol/L (P＜0.05) respectively.Conclusion Chronic hypoxia boosts the release of Ca2+ from sarcoplasmic reticulum and promotes the activity of SOCC and SOCE,leading to [Ca2 +] i elevation and proliferation of rat PASMCs.