ALPHA-1 ADRENERGIC-BLOCKADE INTERACTS WITH DIETARY CARBOHYDRATES ON TRIACYLGLYCEROL METABOLISM IN RATS

The purpose of this study was to evaluate the effects of prazosin, an alpha-1 adrenergic antagonist, on determinants of triacylglycerol metabolism in rats fed chronically diets high in starch or sucrose. Hepatic triacylglycerol secretion rate (HTGSR), lipoprotein lipase in white and brown adipose tissues, red vastus lateralis muscle and heart, as well as serum triacylglycerol concentration, were assessed in the postprandial state, after injection of prazosin or saline. Postprandial triacylglycerolemia was higher in the sucrose-fed than in the starch-fed rats. After the injection of prazosin, triacylglycerol concentrations were decreased in both dietary groups. This effect was more marked in sucrose-fed than in starch-fed rats (diet x blocker interaction: P < 0.0003). HTGSR was higher in rats fed sucrose than in starch-fed rats (+49%, P < 0.01). Prazosin decreased HTGSR (-45%) in the sucrose-fed rats but not in animals fed starch. Lipoprotein lipase activities in brown adipose tissue, vastus lateralis muscle and heart in rats injected with prazosin were enhanced compared with those of the saline-treated rats, but no change was found in enzyme activity in white adipose tissue. This effect of prazosin was independent of the type of diet. These results suggest that prazosin reduced serum triacylglycerol concentrations after food ingestion at least partly by enhancing lipoprotein lipase activity in several tissues. In addition, the prazosin-induced decrease in HTGSR in sucrose-fed rats, which was absent in starch-fed animals, probably accounted for the greater magnitude of the hypotriacylglycerolemic effect of the blocker in animals given sucrose.