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 clearance of chylomicrons (CM) and CM remnants in rats after administration of a fat-containing meal. There was a decrease in clearance of both postprandial CM and exogenous radiolabeled CM in smoke-exposed animals. For exogenous CM, clearance (t(1/2)) increased significantly for both triglyceride and cholesterol labels and correlated with the delay in liver uptake. This decrease in Lipid clearance could not be explained by decreased lipoprotein lipase (LPL) activity because smoke exposure resulted 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 lipase activity was also unchanged in smoke-exposed animals. However, there was a significant delay in the CM remnant uptake into livers isolated from smoke-exposed rats. Thus the delay in CM clearance in smoke-exposed animals cannot be attributed to reduced lipase activities but results from impaired hepatic uptake of CM remnants.