Studies on the plasma glycolipoprotein synthesis by the isolated perfused liver: effect of early choline deficiency

Abstract

Isolated liver perfusion preparations have been used to study the incorporation of glucosamine-1-14C into plasma glycoproteins and glycolipoproteins. The livers obtained from 2-day-choline-deficient rats and perfused with blood obtained from rats on similar dietary treatment showed, compared to controls, an impairment of incorporation of radioactive glucosamine into the trichloroacetic-acid-insoluble protein fraction of plasma during the progress of perfusion. The rate of disappearance of radioactivity in the trichloroacetic-acid-soluble fraction of plasma during perfusion was not affected by choline deficiency. Synthesis of plasma glycolipoproteins as judged by the progressively increased incorporation of radioactivity showed a very significant impairment of synthesis of very low-density (d < 1.006) and low-density (d > 1.006–1.063) glycolipoproteins in early choline deficiency. A similar inhibition of synthesis of plasma proteins of d > 1.21 ("lipid acceptor protein") was observed, whereas the synthesis of high-density lipoproteins (d < 1.063–1.21) was not affected in choline deficiency.The fatty liver in choline deficiency appears to result from an impairment of plasma low-density glycolipoprotein synthesis. A postulation has been made on the stepwise biosynthesis of plasma lipoproteins on the basis of these and earlier studies.