Abstract

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