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Biochem Biophys Res Commun. 2004 Oct 1;322(4):1336-40.

Genetic manipulation of cardiac Na+/Ca2+ exchange expression.

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  • 1Departments of Physiology and Medicine, The Cardiovascular Research Laboratories, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.

Abstract

The Na+/Ca2+ exchanger (NCX) is the primary Ca2+ extrusion mechanism in cardiomyocytes. To further investigate the role of NCX in excitation-contraction coupling and Ca2+ homeostasis, we created murine models with altered expression levels of NCX. Homozygous overexpression of NCX resulted in mild cardiac hypertrophy. Decline of the Ca2+ transient and relaxation of contraction were increased and the reverse mode of NCX was augmented. Overexpression also led to a higher susceptibility to ischemia-reperfusion injury and to a greater ability of NCX to trigger Ca2+-induced Ca2+ release. Furthermore, an increase in peak L-type Ca2+ current was observed suggesting a direct influence of NCX on L-type Ca2+ current. Whereas global knockout of NCX led to prenatal death, a recently generated cardiac-specific NCX knockout mouse was viable with surprisingly normal contractile properties. Expression levels of other Ca2+-handling proteins were not altered. Ca2+ influx in these animals is limited by a decrease of peak L-type Ca2+ current. An alternative Ca2+ efflux mechanism, presumably the plasma membrane Ca2+-ATPase, is sufficient to maintain Ca2+-homeostasis in the NCX knockout mice.

Copyright 2004 Elsevier Inc.

PMID:
15336980
[PubMed - indexed for MEDLINE]
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