Glucose and palmitate uptake in the myocardium of isolated hearts from adrenalectomized cats

Hearts from chronically adrenalectomized (ADX) cats deprived of any steroid support for 9-12 days were isolated and perfused in a Langendorff apparatus at a constant pressure of 95 mm Hg. The perfusion medium was Krebs-Henseleit buffer with either 10 mM glucose or 0.4 mM palmitate complexed to 3 percent albumin. Labeled 14C substrate was used and the transient rate of glucose and palmitate uptake was measured. Oxygen consumption and [14C] palmitate incorporation into CO2, and heart lipids were also measured. ADX hearts showed an enhanced glucose uptake rate compared with controls, 65 +/- 11.3 mumoles/gm to 16.2 +/- 6. However, the qO2 was not significantly different from control hearts. Palmitate uptake, O2 consumption, and 14CO2 were significantly lower in ADX hearts perfused with fatty acid as the energy substrate. Fatty acid uptake decreased from 9.7 +/- 1.0 to 3.6 +/- 1.1 and lipid fractions in the heart showed significant decreases in [14C] palmitate incorporated into triglycerides (p less than 0.001) and monoglycerides (p less than 0.01). The ADX heart does not appear to have any impairment to glucose uptake but does show an impairment to fatty acid uptake. Because the heart uses lipid as the primary energy source, the impairment probably is not the primary factor responsible for cardiac failure in adrenal insufficiency because of its capability of using other available substrates for energy.