Studies for Hepatic Cytosol Factor on Cholesterol Synthesis

Abstract

ln vitro cholesterol syntheses from acetate and mevalonate were not observed in the reaction system with a single liver subcellular fraction, mitochondria, microsomesor cytosol, but in the system with microsomes and cytosol. The factor of cytosol is considered to be carrier proteins and an amount of them may be essential for the overall reaction of cholesterol synthesis.
The significance for cholesterolgenesis was studied using groups of old rats and cholesterol fed rats, whose cholesterol synthesis is decreased, and groups of partial hepatectomy, glucose refed rats and growing rats, whose cholesterol synthesis is increased.
The rate of cholesterol synthesis in hepatic microsomes from cholesterol fed rats and old rats increased in combained incubation with hepatic cytosol from normal or growing rats, while those in the microsomes of normal rats and growing rats decreased with the combination of cytosol from cholesterol fed or old rats. These effects were not brought about by the addition of cholesterol or other inhibitor in cytosol. Therefore, they may be caused either by qualitative or quantitative changes of carrier proteins.
An elevated cholesterol synthesis was observed in those groups of glucose refed rats and partial hepatectomized rats, but the rate of cholesterol synthesis in microsomes of each control was not interfered with cytosol of these treated rats, and the rate in microsomes of the treated rats was not interfered with cytosol of each control. These evidence suggest that the factor of cytosol may be have no relation with the increase of cholesterol synthesis in the groups of partial hepatectomized or glucose refed rats and that cytosol from these control groups contains enough amount of carrier proteins.