[Regulative effects of temperature, intracellular sodium, ATP and pH on I(Na/Ca) of cardiac myocytes].
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 patch-clamp technique was used to record I(Na/Ca) in isolated guinea-pig ventricular myocytes. We found that I(Na/Ca) at 34 degrees C was four times higher than that at 22 degrees C. However, intracellular acidification had no obvious influence on bidirectional I(Na/Ca). At 22~24 degrees C , intracellular ATP depletion and intracellular acidification did not markedly affect bidirectional I(Na/Ca) either. At 34~37 degrees C , 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 did not 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.
Zhou
Hong-Yi
HY
Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
Han
Chong-Yang
CY
Wang
Xiao-Liang
XL
D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology / Q000473:pathology; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000503:physiopathology; D007424:Intracellular Fluid / Q000502:physiology*; D008297:Male; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000502:physiology*; D018408:Patch-Clamp Techniques; D012964:Sodium / Q000502:physiology*; D019831:Sodium-Calcium Exchanger / Q000502:physiology*; D013696:Temperature
D019831:Sodium-Calcium Exchanger; D000255:Adenosine Triphosphate; D012964:Sodium; D002118:Calcium