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Regulative effects of temperature, intracellular sodium, ATP and pH on I_(Na/Ca) of cardiac myocytes

Zhou Hongyi, Han Chongyang, Wang Xiaoliang

Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College.Beijing 100050

Abstract

The Na~(+)-Ca~(2+) exchange is a major pathway for removal of cytosolic Ca~(2+) in cardiac myocytes. To explore the effects of temperature, intracellular Na~(+), ATP and pH on Na~(+)-Ca~(2+) exchange currents （I_(Na/Ca)） of intact guinea-pig myocytes, the whole-cell patchclamp technique was used to record I_(Na/Ca) in isolated guinea-pig ventficular myocytes. We found that I_(Na/Ca) at 34℃ was four times higher than that at 22℃. However, intracellular acidification had no obvious influence on bidirectional I_(Na/Ca). At 22--24℃, intracellular ATP depletion and intracellular acidification did not markedly affect bidirectional I_(Na/Ca) either. At 34--37 ℃. intracellular ATP depletion and intracellular acidification synergistically inhibited the outward and inward currents of I_(Na/Ca), and blocked the inward currents of I_(Na/Ca) more potently than the outward currents of I_(Na/Ca). The effect of ATP on I_(Na/Ca) is temperature-dependent. Intracellular higher sodium increased the outward currents of I_(Na/Ca), however it didn't increase, even sometimes decreased the inward currents of I_(Na/Ca). These results suggest that intracellular ATP depletion and intracellular acidification synergistically impair Ca~(2+) extrusion via forward mode Na~(+)-Ca~(2+) exchange, and intracellular sodium overload increases Ca~(2+) influx via reverse mode Na~(+)-Ca~(2+) exchange, leading to calcium overload respectively.

Key words: sodium-calcium exchanger;Temperature;sodium;patch-clamp technique

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Citing This Article：

Zhou Hongyi, Han Chongyang, Wang Xiaoliang. Regulative effects of temperature, intracellular sodium, ATP and pH on I_(Na/Ca) of cardiac myocytes. Acta Physiol Sin 2006; 58 (2): (in Chinese with English abstract).