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 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.
Subject(s)
Animals , Male , Adenosine Triphosphate , Physiology , Calcium , Metabolism , Guinea Pigs , Heart Ventricles , Cell Biology , Pathology , Hydrogen-Ion Concentration , Hypoxia , Intracellular Fluid , Physiology , Myocytes, Cardiac , Metabolism , Physiology , Patch-Clamp Techniques , Sodium , Physiology , Sodium-Calcium Exchanger , Physiology , TemperatureABSTRACT
<p><b>OBJECTIVE</b>To study the effect of CACNA1H gene mutation G773D on calcium channel function.</p><p><b>METHODS</b>By the overlap extension PCR we introduced G773D mutation into a human Cav3.2acDNA for constructing the mutant. And then using whole cell clamp technique, we studied the alterations of channel behavior in transfected HEK-293 cells.</p><p><b>RESULTS</b>There were no difference in kinetics of activation and inactivation of calcium channel between wild type and mutant. However comparing with the wild-type Cav3.2 channel, G773D mutant could increase the calcium current density significantly.</p><p><b>CONCLUSION</b>CACNA1H gene G773D mutation is able to increase calcium current and neuronal excitability.</p>