Differentiation of cholesterol compartments in the immature chick testis.

The behaviour of testicular free and esterified cholesterol during early posthatching development and after stimulation with human chorionic gonadotrophin was studied in the immature chick using combined electron microscope and biochemical techniques. The interstitial cells represented about 65% of the testicular tissue and the lipid droplets in the cytoplasm of these cells were considerably depleted after HCG treatment. The lipid droplets isolated from 7-day-old testis contained about 95% of the total esterified cholesterol which was significantly reduced in the testis and isolated lipid droplets after HCG stimulation. The bulk of free cholesterol was associated with the microsomal fraction whose membranes and cholesterol content increased during normal maturation and after gonadotrophin-induced differentiation.