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Turnover rate of the cardiac Na(+)‐Ca2+ exchanger in guinea‐pig ventricular myocytes.
Author(s) -
Powell T,
Noma A,
Shioya T,
Kozlowski R Z
Publication year - 1993
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1993.sp019935
Subject(s) - chemistry , biophysics , hyperpolarization (physics) , guinea pig , myocyte , membrane potential , cytosol , calcium , q10 , voltage clamp , analytical chemistry (journal) , medicine , anatomy , biochemistry , stereochemistry , chromatography , biology , enzyme , respiration , organic chemistry , nuclear magnetic resonance spectroscopy
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.