慢性低氧后钙转运的变化

目的　观察大鼠慢性低氧后心肌钙转运的变化。方法　将大鼠放置于 1 0 %氧环境下 4周 ,分离正常及慢性缺氧大鼠的右心室肌细胞 ,用光谱荧光法测定电刺激和咖啡因引起的细胞内 [Ca2 ]i瞬变 ,并测定肌浆网膜上的Ca2 -ATP酶 (SERCA)和ryanodine受体 (RyR)蛋白水平。结果　低氧后电刺激和咖啡因引起的细胞内 [Ca2 ]i瞬变的幅度降低且时程延长 ,RyR水平无明显改变 ,但SERCA已显著减少。结论　Ca2 -ATP酶活性和蛋白水平的降低是低氧钙转运异常的主要原因

THE CHANGES OF CALCIUM HOMEOSTASIS IN RAT CARDIOMYOCYTES FOLLOWING CHRONIC HYPOXIA

Objective There is evidence suggesting that the Ca 2 handling may be altered following chronic hypoxia. The main purpose of the present study was to determine the intracellular calcium handling in the rat heart during chronic hypoxia. Spectrofluorometry was used to measure intracellular calcium ([Ca 2 ] i) responses to electric field and caffeine stimulation in single myocytes isolated from right ventricles of chronically hypoxic (CH) rats breathing 10% oxygen for 4 weeks and those of the age-matched controls. The protein expression of sarcoplasmic reticulum Ca 2 -ATPase (SERCA) and its ryanodine receptor (RyR) were measured. It was found that Ca 2 homeostasis reach a new equilibrium after 4 weeks of CH. The Ca 2 content in SR as indicated by the amplitude of the caffeine induced [Ca 2 ] i transient, was reduced, but the cytosolic Ca 2 remained the same. The amplitude and decay of the electrically induced [Ca 2 ] i transient were also reduced, indicating the SR functions namely, release of Ca 2 from SR during excitation contraction coupling and uptake of Ca 2 via the Ca 2 ATPase back to SR, were reduced. The time of 50% decline of the caffeine induced [Ca 2 ] i transient, which indicates the Na -Ca 2 exchange activity, was also reduced. Further study showed that expression of SERCA was suppressed by CH while expression of RyR was not altered. The results indicate that the attenuated Ca 2 -ATPase is mainly responsible for impaired Ca 2 handling in CH.