Effects of phthalazinol (EG 626) on arterial lipolytic enzyme activities in the rat.

Phthalazinol (EG 626), a thromboxane A2 antagonist and cyclic AMP phosphodiesterase inhibitor, has been shown to prevent the atherosclerosis induced in cholesterol fed rabbits. In an attempt to clarify the antiatherosclerotic mechanism, the effects of this compound on the lipolytic enzyme activities (cholesterol esterase and lipoprotein lipase) of rat aorta were examined in vivo. Administration of EG 626 (100-200 mg/kg, per os, daily, 1-2 weeks) affected neither the aortic lysosomal cholesterol esterase nor the acid phosphatase activity, whereas the lipoprotein lipase activity was signficantly decreased by the treatment. These results suggest that with an elevation in HDL-cholesterol, a decrease in lipoprotein lipase activity after ingestion of EG 626 might contribute, at least to some extent, to the prevention of arterial lipid accumulation.