Abstract
In ferret ventricular myocytes the rate of intracellular Ca concentration [Ca]i decline and relaxation is remarkably fast (compared with rabbit and rat) under conditions where both the sarcoplasmic reticulum Ca uptake and Na/Ca exchange are inhibited. Here we explore the possibility that this rapid [Ca]i decline in ferret cells is attributable to the sarcolemmal Ca ATPase by using carboxyeosin (a potent inhibitor of the sarcolemmal Ca-ATPase). We compare the effects of carboxyeosin with those of elevated extracellular [Ca] ([Ca]o) (a thermodynamic approach to limit Ca transport by the sarcolemmal Ca ATPase). In rabbit cells, carboxyeosin and high [Ca]o slowed [Ca]i decline similarly and both virtually abolished [Ca]i decline when mitochondrial Ca uptake was also inhibited. In ferret cells, carboxyeosin treatment produced these same effects on [Ca]i decline, but high [Ca]o did not mimic them. Moreover, only in carboxyeosintreated ferret cells did additional inhibition of mitochondrial Ca uptake nearly abolish [Ca]i decline. We conclude that, carboxyeosin loading can inhibit the sarcolemmal Ca-ATPase in intact myocytes; that this pump seems likely to be responsible for the much faster relaxation observed in ferret cells after block of SR Ca accumulation and Na/Ca exchange transport and that the sarcolemmal Ca pump apparently has different characteristics in rabbit and ferret ventricular myocytes.
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Present address: Centro de Engenharia Biomédica Caixa Postal 6040, Universidade Estadual de Campinas (UNICAMP), 13081 Campinas, SP, Brazil
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Bassani, R.A., Bassani, J.W.M. & Bers, D.M. Relaxation in ferret ventricular myocytes: role of the sarcolemmal Ca ATPase. Pflugers Arch. 430, 573–578 (1995). https://doi.org/10.1007/BF00373894
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DOI: https://doi.org/10.1007/BF00373894