INTRACELLULAR-PH REGULATION IN FERRET VENTRICULAR MUSCLE - THE ROLE OF NA-H EXCHANGE AND THE INFLUENCE OF METABOLIC SUBSTRATES
INTRACELLULAR-PH REGULATION IN FERRET VENTRICULAR MUSCLE - THE ROLE OF NA-H EXCHANGE AND THE INFLUENCE OF METABOLIC SUBSTRATES
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DOI：
10.1161/01.res.68.1.150
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发表时间：
1991-01-01
影响因子：
20.1
通讯作者：
MCGUIGAN, JAS
中科院分区：
文献类型：
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作者：
BLATTER, LA;MCGUIGAN, JAS
在无重碳酸盐的台氏液中，用pH和钠选择性微电极研究了雪貂心室肌细胞的pH调节。瞬时应用NH4Cl(10或20 mmol/L)可产生酸负荷。多次应用NH4Cl仍可完全恢复酸负荷，但Na-H交换阻断剂阿米洛利(0.75或1 mmol/L)可增加酸化并抑制恢复。细胞内钠浓度的测量显示，在应用NH4Cl期间，细胞内钠浓度短暂下降，在酸化恢复期间，细胞内钠浓度短暂上升，高于对照组。这种增加被阿米洛利抑制。细胞内钠负荷(Strophanthidin[低钙低钾Tyrode‘s溶液])最初不会引起细胞内pH(I)的变化，但在这种情况下阿米洛利引起的酸化更大。将细胞外钠浓度从15 5降至5或降至1 5 mmol/L可引起细胞酸化。胞外pH(pH(O))从6.4时至8.4时，pH(I)沿同一方向的平均线性变化为0.085个pH(I)单位/pH(O)单位。用NH4Cl法和阿米洛利阻断质子排出机制测得的平均细胞内缓冲容量为36+/-15 mmolpH-1.l-1(Mean+/-SD)，约为先前估计的一半。将代谢底物从葡萄糖改变为丙酮酸，可使酸化0.21个pH单位。这可以被α-氰基-4-羟基肉桂酸酯部分阻断，这一发现与心室细胞中存在丙酮酸-H+共转运和/或丙酮酸-OH-反向转运系统一致。本研究结果表明，心肌细胞能有效地缓冲氢离子，安娜-H交换系统在调节pH(I)中起主要作用。
Aspects of pH regulation in ferret ventricular cells have been investigated by using pH- and sodium-selective microelectrodes in bicarbonate-free Tyrode's solution. An acid load was produced by the transient application of NH4Cl (10 or 20 mmol/l). A complete recovery from an acid load was still observed after multiple applications of NH4Cl, but amiloride (0.75 or 1 mmol/l), a blocker of the Na-H exchanger, increased the acidification and inhibited the recovery. Measurements of intracellular sodium concentration showed a transient decrease during the application of NH4Cl and a transient increase above control values during recovery from acidification. This increase was inhibited by amiloride. Intracellular sodium loading (strophanthidin [low calcium-low potassium Tyrode's solution]) did not initially cause an intracellular pH (pH(i) change, but the acidification induced by amiloride under those circumstances was larger. Reducing extracellular sodium concentration from 155 to 5 or to 1.5 mmol/l caused an acidification. Changing extracellular pH (pH(o)) from 6.4 to 8.4 caused an average linear change in pH(i) in the same direction of 0.085 pH(i) units/pH(o) units. The mean intracellular buffering capacity measured with the NH4Cl method and with the proton extrusion mechanism blocked by amiloride was 36 +/- 15 mmol pH-1.l-1 (mean +/- SD), approximately half that of previous estimations. Changing the metabolic substrate from glucose to pyruvate in the superfusing solution caused an acidification of 0.21 pH units. This could be partially blocked by alpha-cyano-4-hydroxycinnamate, a finding consistent with a pyruvate-H+ cotransport and/or a pyruvate-OH- countertransport system being present in ventricular cells. The results of the present study show that ventricular cells can effectively buffer hydrogen ions and that an Na-H exchange system plays a major role in the regulation of pH(i).