The effects of inhibition of the sarcolemmal Ca-ATPase on systolic calcium fluxes and intracellular calcium concentration in rat ventricular myocytes.
The effects of carboxyeosin, an inhibitor of the sarcolemmal Ca-ATPase, were studied on intracellular Ca and membrane currents in isolated rat ventricular myocytes. In the absence of carboxyeosin, 150-ms-duration depolarizing pulses from -40 to 0 mV resulted in an L-type Ca current on depolarization and a Na-Ca exchange "tail" current on repolarization. The calculated entry of Ca on the L-type current was 1.3 times greater than the efflux via the Na-Ca exchange. The addition of carboxyeosin (20 microM) resulted in either an increase of the Na-Ca exchange current or a decrease of the L-type Ca current such that the Ca entry and efflux were exactly equal. These results suggest that, under control conditions, a carboxyeosin-sensitive Ca-ATPase contributes about 24% of the total Ca efflux from the cell and, therefore, that the sarcolemmal Ca-ATPase has a significant role in regulation of sarcolemmal Ca fluxes.
Choi
H S
HS
Department of Veterinary Preclinical Sciences, University of Liverpool, Liverpool L69 3BX, UK.
Eisner
D A
DA
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D004553:Electric Conductivity; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004801:Eosine Yellowish-(YS) / Q000494:pharmacology; D006352:Heart Ventricles / Q000378:metabolism; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D012508:Sarcolemma / Q000201:enzymology*; D013599:Systole
D015220:Calcium Channels; D004791:Enzyme Inhibitors; D000252:Calcium-Transporting ATPases; D002118:Calcium; D004801:Eosine Yellowish-(YS)