Uptake of cholesterol from the very low density lipoprotein or its remnants by the perfused rat liver.
[3H]Cholesterol labelled very low density lipoproteins ([3H]chol-VLDL) were prepared to study the hepatic uptake of cholesterol associated with VLDL and its remnants in the perfused liver system. [3H]Chol-VLDL was incubated with rat postheparin plasma to produce labelled remnants in vitro. The degree of lipolysis of [3H]chol-VLDL depended on the ratio of triacylglycerols to lipase in the incubation medium. Therefore, the produced remnant of d less than 1.019 g. mL-1 had a variable lipid composition depending on the degree of lipolysis. [3H]Chol-VLDL or its remnants were added to liver perfusate and the radioactivity remaining in the perfusate was measured. The kinetic disappearance of [3H]chol-VLDL and its remnants in the perfused liver system indicated that remnant of d less than 1.019 g. mL-1 was taken up by the liver faster than the original VLDL preparation (t1/2 of 8 min vs. 51 min). Appearance of the label in bile during the perfusion was significantly faster when livers were perfused with [3H]chol-VLDL remnants as opposed to uncatabolized [3H]chol-VLDL. The results indicate that first of all, VLDL remnants produced in vitro and reisolated at density less than 1.019 g.mL-1 do not have a fixed lipid composition but a rather variable one depending on the degree of lipolysis. Secondly, the rat liver may preferentially recognize this VLDL remnant of d less than 1.019 g.mL-1 and take it up more readily than uncatabolized VLDL. Finally when equimolar amount of cholesterol from VLDL or VLDL remnants are circulated in the liver perfusion, the VLDL remnants convey a significantly greater mass of cholesterol in the bile.
D000818:Animals; D001053:Apolipoproteins / Q000378:metabolism; D001056:Apolipoproteins C; D002784:Cholesterol / Q000378:metabolism*; D015243:Cholesterol, VLDL; D006493:Heparin / Q000494:pharmacology; D008071:Lipoprotein Lipase / Q000378:metabolism; D008079:Lipoproteins, VLDL / Q000032:analysis / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D010477:Perfusion; D051381:Rats; D014280:Triglycerides / Q000032:analysis
D001053:Apolipoproteins; D001056:Apolipoproteins C; D015243:Cholesterol, VLDL; D008079:Lipoproteins, VLDL; D014280:Triglycerides; D006493:Heparin; D002784:Cholesterol; D008071:Lipoprotein Lipase