Myocardial substrate utilization in perfused hearts isolated from adrenalectomizedcats

Abstract

Isolated hearts form chronically adrenalectomized cats were perfused with Krebs-Henseleit buffer plus either glucose (10mM) or palmitate (0.4 mM) under various conditions of constant pressure and constant flow. Glucose uptake in adrenalectomizedhearts was not diminished from control values under conditions of constant pressure, constant flow, anoxia, or insulin stimulation. Palmatic acid uptake and oxygen consumption were significantly reduced (P less than 0.02) in adrenalectomized hearts. This diminished fatty acid utilization was also reflected in a significantly lower CO'2 production and incorporation of the palmitate into myocardial triglycerides. The decreased fatty acid uptake by adrenalectomized cat hearts may represent aserious defect in myocardial metabolism since lipids are the major energy substrate forthe heart. Whether the defect occurs in fatty acid transport or activation cannot beelucidated by this study. However, it is unlikely that this defect has a major contributory effect on the dysfunction of adrenalectomized hearts since the myocardium iscabable of using other energy substrates readily.