AJP - Cell Physiology, Vol 269, Issue 3 C632-C640, Copyright © 1995 by American Physiological Society

ARTICLES

[Ca2+]i transients in hypertensive and postinfarction myocytes

X. Q. Zhang, R. L. Moore, T. Tenhave and J. Y. Cheung
Department of Medicine, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033, USA.

Changes in intracellular calcium concentration ([Ca2+]i) in paced fura 2-loaded myocytes isolated from Sham, renovascular hypertensive (Hyp), and myocardial-infarcted (MI) rats were examined. Compared with controls, Hyp myocytes paced at physiological rates had similar systolic but elevated diastolic [Ca2+]i. By contrast, systolic [Ca2+]i was significantly lower and diastolic [Ca2+]i higher in MI myocytes. The different patterns of alterations in [Ca2+]i dynamics in Hyp and MI myocytes may partly explain predominantly diastolic dysfunction in hypertensive hearts and systolic dysfunction in hearts surviving MI. In the presence of 1 microM isoproterenol, both Hyp and MI myocytes had much lower systolic [Ca2+]i when compared with their respective controls. Isoproterenol restored the elevated diastolic [Ca2+]i in Hyp myocytes toward normal but had no effect on the intrinsic differences in diastolic [Ca2+]i between Sham and MI myocytes. The observation that isoproterenol lowers diastolic [Ca2+]i in Hyp myocytes toward normal may provide a cellular mechanism for the lack of efficacy of beta-adrenergic blockers to improve diastolic compliance in patients with hypertensive hypertrophic cardiomyopathy.

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