Turnover rate of the cardiac Na(+)-Ca2+ exchanger in guinea-pig ventricular myocytes.
1. Single guinea-pig ventricular myocytes were voltage clamped using the whole-cell configuration of the patch-clamp technique and membrane current generated by the Na(+)-Ca2+ exchange mechanism recorded. 2. Rapid increases in cytosolic free calcium ([Ca2+]i) evoked by flash photolysis of either nitr-5 or DM-nitrophen resulted in current relaxations, arising from a redistribution of exchanger carrier conformations induced by the changes in [Ca2+]i. 3. Relaxation time constants were temperature dependent with a temperature coefficient over a 10 degrees C range (Q10) of approximately 3 and also voltage dependent, decreasing on hyperpolarization for membrane potentials in the range +40 to -80 mV. 4. The experimental results are consistent with consecutive exchange models having electrogenic Na+ translocation steps, together with a site density and turnover rate similar to that for the Na(+)-K+ pump.
Powell
T
T
University Laboratory of Physiology, Oxford.
Noma
A
A
Shioya
T
T
Kozlowski
R Z
RZ
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D005071:Evoked Potentials / Q000528:radiation effects; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000378:metabolism; D066298:In Vitro Techniques; D017136:Ion Transport / Q000528:radiation effects; D007700:Kinetics; D008564:Membrane Potentials; D008955:Models, Cardiovascular; D009206:Myocardium / Q000378:metabolism*; D010782:Photolysis; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger; D013696:Temperature
D002352:Carrier Proteins; D019831:Sodium-Calcium Exchanger; D012964:Sodium; D002118:Calcium