Blatter L A, McGuigan J A
Department of Physiology, University of Berne, Switzerland.
Circ Res. 1991 Jan;68(1):150-61. doi: 10.1161/01.res.68.1.150.
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 (pHi) 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 (pHo) from 6.4 to 8.4 caused an average linear change in pHi in the same direction of 0.085 pHi units/pHo 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 pHi.
利用pH和钠选择性微电极，在无碳酸氢盐的台氏液中对雪貂心室肌细胞的pH调节方面进行了研究。通过短暂施加氯化铵（10或20 mmol/L）产生酸负荷。多次施加氯化铵后仍可观察到酸负荷的完全恢复，但钠-氢交换体阻滞剂氨氯地平（0.75或1 mmol/L）增加了酸化程度并抑制了恢复。细胞内钠浓度测量显示，在施加氯化铵期间短暂降低，在从酸化恢复期间短暂升高至对照值以上。这种升高被氨氯地平抑制。细胞内钠负荷（毒毛花苷 [低钙低钾台氏液]）最初并未引起细胞内pH（pHi）变化，但在这些情况下氨氯地平诱导的酸化更大。将细胞外钠浓度从155 mmol/L降至5或1.5 mmol/L会导致酸化。将细胞外pH（pHo）从6.4变为8.4会导致pHi在相同方向上平均线性变化0.085 pHi单位/pHo单位。用氯化铵方法并在氨氯地平阻断质子外排机制的情况下测得的平均细胞内缓冲能力为36±15 mmol·pH⁻¹·L⁻¹（平均值±标准差），约为先前估计值的一半。在灌流液中将代谢底物从葡萄糖改为丙酮酸会导致0.21个pH单位的酸化。这可被α-氰基-4-羟基肉桂酸部分阻断，这一发现与心室肌细胞中存在丙酮酸-H⁺共转运和/或丙酮酸-OH⁻逆向转运系统一致。本研究结果表明，心室肌细胞可有效缓冲氢离子，且钠-氢交换系统在pHi调节中起主要作用。
