Effects of phthalazinol (EG 626) and pyridinolcarbamate (Anginin) on lipolytic enzyme activities in rat adipose tissue -in vivo and in vitro-.

Effects of Phthalazinol (EG 626), a cyclic AMP phosphodiesterase inhibitor, a thromboxane A2 antagonist and an antiatherosclerotic agent was examined regarding lipolytic enzyme activities in rat epididymal adipose tissue. The effect of Pyridinolcarbamate (Anginin) was concomitantly examined. There was a significant decrease in serum triacylglycerol levels in rats given EG 626 (100-500 mg/kg), p.o. for 1-3 weeks. In adipose tissue from EG 626 treated rats, the basal and adrenalin induced lipolysis, and cholesterylester hydrolase activity were markedly enhanced, while the phosphodiesterase activity was decreased. Anginin treatment had no effect either on the serum lipid levels or the cholesterylester hydrolase activity. An elevation in cholesterylester hydrolase activity and lipolysis by EG 626 was observed both in vivo and in vitro. Incubation of the adipose tissue with 0.229 mM of EG 626 or 0.603 mM of theophylline induced a lipolysis equivalent to that seen with 2.7 x 10(-2) mM of adrenalin. These results indicate that EG 626 exerted marked effects on lipolysis and cholesterylester hydrolase activity, probably through inhibition of phosphodiesterase. Possible contributions of the enhanced cholesterylester hydrolase activities to the antiatherogenic effect were discussed.