EXPOSURE TO CIGARETTE-SMOKE DELAYS THE PLASMA-CLEARANCE OF CHYLOMICRONS AND CHYLOMICRON REMNANTS IN RATS

We investigated the effects of cigarette smoke exposure on the clearan ce of chylomicrons (CM) and CM remnants in rats after administration o f a fat-containing meal. There was a decrease in clearance of both pos tprandial CM and exogenous radiolabeled CM in smoke-exposed animals. F or exogenous CM, clearance (t(1/2)) increased significantly for both t riglyceride and cholesterol labels and correlated with the delay in li ver uptake. This decrease in Lipid clearance could not be explained by decreased lipoprotein lipase (LPL) activity because smoke exposure re sulted in a significant increase in LPL activity. When the hydrolysis of CM by endothelial LPL was tested in a heart perfusion system, there was no difference in CM hydrolysis between the two groups. Hepatic li pase activity was also unchanged in smoke-exposed animals. However, th ere was a significant delay in the CM remnant uptake into livers isola ted from smoke-exposed rats. Thus the delay in CM clearance in smoke-e xposed animals cannot be attributed to reduced lipase activities but r esults from impaired hepatic uptake of CM remnants.