Myocardial contractile efficiency and oxygen cost of contractility are preserved during transition from compensated hypertrophy to failure in rats with salt-sensitive hypertension
Abstract
In Dahl-Iwai rats, salt-sensitive hypertension causes concentric left ventricular hypertrophy (LVH) at the age of 11 weeks, which is followed by LV dilatation with global hypokinesis and pulmonary congestion, ie, LV failure (LVF), at 16 to 18 weeks of age. To address the question of whether the cardiac remodeling from LVH to LVF is associated with modulations of mechanoenergetic properties, we serially measured the LV pressure-volume area (PVA) and myocardial oxygen consumption (MVO2) in isolated, isovolumically contracting hearts from this animal model. The end-systolic pressure-volume relationships obtained by stepwise changes of the LV volume were fit into a binominal regression model, which provided a value of LV contractility (E(es)) and a volume intercept (V0). A slope (the reciprocal of the LV contractile efficiency) and a PVA-independent MVO2 were determined by a regression analysis of the MVO2-PVA relation. The procedure was repeated at different Ca2+ concentrations in perfusate to estimate the oxygen cost of contractility (dMVO2/dE(es)). The MVO2 was further evaluated during K+-induced cardiac arrest to delineate the basal metabolism, which was independent of the E-C coupling. During the transition from LVH to LVF, th...Continue Reading
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