Cholesterol and lipoprotein metabolism
Onajobi, Funmilayo D.
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The incorporation of 14C-cholesterol synthesized from (2-14C)DL-MVA into rat serum lipoproteins by the perfused rat liver and the subcellular fractions of rat liver was studied. It was found that the perfused liver incorporated 14C-cholesterol into α2-lipoprotein faster than into any other serum lipoprotein, whereas rat liver microsomes, in the presence of the cell sap, preferentially incor¬ porated 14C-cholesterol into α1-lipoprotein. Addition of serum to an in vitro lipoprotein synthesizing incubation mixture apparently inoreased the proportion of newly synthesized cholesterol incorporated into lipoproteins, but at high concentrations of serum, there was a decrease in the incorporation of (2-14C)-MVA into cholesterol. Detailed analysis of the radioactive lipid produots of the incubation mixture showed that, concomitant with the decrease in cholesterol synthesis, there was an accumulation of radioaotive squalene. Both rat and human serum oontained the squalene accumulating factor. Pretreatment of the serum by dialysis, heat, reaotion with PCMB, NEM, and addition of excess co-factors to the incubation mixture, all failed to annul the squalene accumulating effect of serum.