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Hypertrophied myocardium is more dependent on extracellular calcium than the normal cardiac muscle

Reginaldo de Barros, Leonardo A.M. Zornoff, Henrique B. Ribeiro, Marina P. Okoshi, Carlos R. Padovani, Flavio F. Aragon, Antonio C. Cicogna

Med Sci Monit 2010; 16(8): BR

ID: 881100

Published: 2010-08-01

Background:    The aim of this study was to analyze stable hypertrophied myocardial function and its response to inotropic maneuvers in rats submitted to renovascular hypertension for a 10-week period (RHT group, n=10).
    Material/Methods:    Myocardial performance was studied in isolated left ventricle papillary muscles in isometric contraction under the following conditions: at postrest contraction of 30 seconds (PRC), at extracellular calcium (ECa2+) chloride concentration of 1.25 and 5.20mM, and after beta-adrenergic stimulation with 10–6 M isoproterenol (ISOP).
    Results:    The results were compared with normotensive Wistar controls rats (C group, n=10). In basal condition, resting tension, and contraction time (TPT) were greater, while relaxation time (RT50) tended to be longer in RHT than C group. PRC and ISOP promoted a similar change in muscle function response intensity (delta) in both groups. ECa2+ shift did not change TPT in the C group and decreased TPT in the RHT animals; delta was different between these groups. RT50 increased in C and decreased in RHT, both without statistical significance; however, delta was different.
    Conclusions:    These results suggest that hypertrophied myocardial dysfunction may be attributed to changes in intracellular calcium cycling.

Keywords: Myocardial Contraction - drug effects, Male, Isoproterenol - pharmacology, Isometric Contraction - drug effects, Hypertrophy, Extracellular Space - metabolism, Calcium - pharmacology, Blood Pressure - drug effects, Animals, Myocardium - pathology, Rats, Rats, Wistar, Rest - physiology, Systole - drug effects