pH改变对心肌细胞内Ca~(2 )浓度和细胞长度的影响

目的 :探讨细胞内 pH(pHi)改变对心肌细胞内Ca2 浓度 ([Ca2 ]i)和细胞长度的影响。方法 :心肌细胞内分别灌注 2 0mmol/L丙酸钠和 15mmol/LNH4Cl,建立细胞内酸碱中毒模型。荧光指示剂indo 1和SNARF 1载入大鼠心肌细胞内 ,用荧光显微镜同时测定心肌 [Ca2 ]i、pHi 和细胞长度。结果 :细胞内酸中毒早期 ,收缩期和舒张期[Ca2 ]i 轻度增加 ,细胞缩短 (CS)降低 ,细胞长度增加 ,心肌纤维对Ca2 的敏感性和CS/ [Ca2 ]i 降低 (P <0 .0 1) ;碱中毒时 ,收缩期和舒张期 [Ca2 ]i 均较对照组降低 ,CS增加 ,细胞长度变短 ,心肌纤维对Ca2 的敏感性和CS/[Ca2 ]i 增加 (P <0 .0 1)。结论 :酸中毒早期 [Ca2 ]i 和细胞长度增加 ,碱中毒时 [Ca2 ]i和细胞长度降低。酸、碱中毒对Ca2 敏感性的影响并非线性关系 ,即单位 pHi变化时酸中毒对敏感性的影响较碱中毒小

EFFECT OF CHANGES IN pH ON INTRACELLULAR Ca~(2 )AND CELL LENGTH OF MYOCYTES

Aim: To examine the effects of pH i on [Ca 2 ] i , cell length and Ca 2 sensitivity of myofilaments in rat myocyte. Methods: We used microscopic spectral imaging approach to monitor simultaneously [Ca 2 ] i, pH i and cell length with fluorescent indicator indo 1 and SNARF 1 in isolated single rat myocyte. Results: Exposure of cell to 20 mmol/L Sodium Propionate induced an intracellular acidosis which increased slightly systolic and diastolic [Ca 2 ] i, decreased the cell shortening (CS) and Ca 2 sensitivity of myofilament ( P <0.01). Exposure of cell to 15 mmol/L NH 4Cl induced an intracellular alkalosis which decreased systolic and diastolic [Ca 2 ] i, increased the cell shortening and Ca 2 sensitivity of myofilament ( P <0.01). Conclusions: In the early time of acidosis, [Ca 2 ] i, as well as cell length increases repectively. While alkalosis, [Ca 2 ] i and cell length decreases respectively. The effect of acidosis and alkalosis on Ca 2 sensitivity presents non linear relationship, i.e. the effect of acidosis on sensitivity, caused by pHi change, is less than that of alkalosis.