[Ca2+]i transients in hypertensive and postinfarction myocytes.
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.
Zhang
X Q
XQ
Department of Medicine, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033, USA.
Moore
R L
RL
Tenhave
T
T
Cheung
J Y
JY
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002304:Cardiac Pacing, Artificial; D002469:Cell Separation; D003971:Diastole; D005260:Female; D006973:Hypertension / Q000378:metabolism* / Q000473:pathology; D007425:Intracellular Membranes / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D009203:Myocardial Infarction / Q000378:metabolism* / Q000473:pathology; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D011916:Rats, Inbred F344; D013599:Systole
D000318:Adrenergic beta-Agonists; D007545:Isoproterenol; D002118:Calcium