Control of lipolysis in triglyceride-enriched rat hearts

Hormonal and metabolic regulation of endogenous triglyceride hydrolysis was studied in triglyceride-enriched hearts obtained from rats fed 3 days with a trierucate-rich diet. Endogenous lipolysis was determined by measuring glycerol release during in vitro perfusion of the hearts. It appeared that there was a direct relation between the contractile state of the heart, the rate of glycerol release in the coronary effluent and the Ca2+ concentration in the perfusion medium. During Ca2+-free perfusion, 2,4-dinitrophenol stimulated oleate oxidation and this, as well as the addition of 2 x 10(-7) M glucagon, induced a marked stimulation of lipolysis. Insulin did not affect glucagon- and norepinphrine-stimulated lipolysis during substrate-free perfusion. The presented experiments point out that in lipid-enriched rat hearts the activity of the tissue lipase may be controlled by the rate of beta-oxidation and re-esterification of the liberated fatty acid, as well as by a shift to utilization of carbohydrate instead of fatty acids for energy supply.