POSSIBLE ROLE OF LIPOPROTEIN-LIPASE IN THE REGULATION OF ENDOGENOUS TRIACYLGLYCEROLS IN THE RAT-HEART

Adrenaline [epinephrine] has a biphasic effect on intracellular lipoprotein lipase activity and on endogenous triacylglycerol content in the heparin-perfused rat heart. A high concentration of adrenaline (1 .mu.M in the perfusion buffer) activated endogenous lipoprotein lipase activity and, at the same time, decreased intracellular triacylglycerol stores. A low concentration (0.005 .mu.M adrenaline) inhibited intracellular lipoprotein lipase activity. Under these conditions, cardiac triacylglycerol content was elevated above control values. Perfusing the heart with high and low concentrations of 3-isobutyl-1-methylxanthine elicited a biphasic effect on endogenous lipoprotein lipoprotein lipase activity and triacylglycerol content similar to that seen with adrenaline treatment. The effect of adrenaline on intracellular lipoprotein lipase activity appears to be mediated by cAMP through protein kinase. A possible role for intracellular lipoprotein lipase in the regulation of endogenous triacylglycerol in rat heart is proposed.