Key result
Blockade of the Na(+)-Ca2+ exchanger reduced the rate of intracellular Ca2+ decline by 47%, while blockade of SERCA reduced it by 23% in rabbit inferior vena cava smooth muscle.
In rabbit inferior vena cava smooth muscle, the sarcoplasmic reticulum contributes to Ca2+ extrusion via SERCA arranged in series with Na+-Ca2+ exchange.
Should not change clinical practice; extends animal data on vascular Ca2+ extrusion but leaves human relevance open.
Ca2+ extrusion from rabbit inferior vena cava smooth muscle was studied using ratiometric fura 2 fluorimetry. Concomitant blockade of the plasma membrane Ca(2+)-adenosinetriphosphatase (ATPase; PCMA), Na(+)-Ca2+ exchanger, and sarcoendoplasmic reticulum Ca(2+)-ATPase (SERCA) completely prevented the decline in intracellular Ca2+ concentration ([Ca2+)]i) normally observed when Ca2+ is removed from the extracellular space (ECS) after stimulated Ca2+ influx. Blockade of the Na(+)-Ca2+ exchanger by removal of external Na+ reduced the rate of [Ca2+]i decline by 47%. Blockade of SERCA with cyclopiazonic acid reduced it by 23%, and this was not additive to the effects of Na+ removal. Exposure to nominally Ca(2+)-free solution prevented the sarcoplasmic reticulum (SR) from reloading only if the Na(+)-Ca2+ exchanger was operational. Our results can be explained by an SR contribution to Ca2+ extrusion in which SERCA is arranged in series with Na(+)-Ca2+ exchange.
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Nazer et al. (1998) studied this question. Blockade of Na(+)-Ca2+ exchanger and SERCA was evaluated on Rate of intracellular Ca2+ decline. Blockade of the Na(+)-Ca2+ exchanger reduced the rate of intracellular Ca2+ decline by 47%, while blockade of SERCA reduced it by 23% in rabbit inferior vena cava smooth muscle.
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