Characterization of high-density lipoprotein binding to guinea pig hepatic membranes: Effects of dietary fat quality and cholesterol feeding

The effects of dietary fat quality and cholesterol intake on expression of guinea pig hepatic membrane high-density lipoprotein (HDL) binding sites were studied. Animals were fed semisynthetic diets containing 7.5% (wt/wt) of either corn oil (CO), olive oil (OL), or lard. The cholesterol diet was prepared by incorporating 0.25% recrystallized cholesterol into standard guinea pig chow. Plasma cholesterol levels of guinea pigs on the CO diet were significantly lower ( P < .02) than animals on the OL or lard diets. HDL cholesterol levels did not differ between the polyunsaturated, monounsaturated, and saturated dietary fat groups. Guinea pigs on the high cholesterol diet had increased total and HDL cholesterol levels compared with animals on the chow diet ( P < .01). Initial studies demonstrated that HDL binding to hepatic membranes was temperature-dependent. A threefold increase in binding was observed when assays were performed at 37°C, as compared with 4°C, for all membrane preparations. Dietary fat quality and dietary cholesterol intake significantly altered HDL binding to hepatic membranes with increased HDL binding to membranes of animals fed polyunsaturated fat and the high cholesterol diet. At 37°C, HDL binding to hepatic membranes of CO-fed animals was 26% and 46% higher than for membranes of OL- and lard-fed guinea pigs, respectively. A high cholesterol intake increased HDL binding by 24% at both 4°C and 37°C. Scatchard analysis demonstrated that while membrane affinity for HDL (K d) was not affected by diet, changes did occur in the total number of HDL binding sites. B max values were significantly higher ( P < .05) for membranes from cholesterol- and CO-fed guinea pigs. These data demonstrate that in the guinea pig, HDL binding to hepatic membranes is regulated by both dietary fat quality and dietary cholesterol.