Hypercholesterolaemia, hypotriacylglycerolaemia and increased lipoprotein lipase activity following orchidectomy in rats.

Plasma lipoproteins, faecal cholesterol excretion, and activities of lecithin: cholesterol acyltransferase (LCAT) hepatic lipase (HL), and lipoprotein lipase (LPL) were determined in castrated rats, in rats treated with testosterone propionate after castration, and in sham-operated controls. Compared to control rats, whole-plasma total cholesterol (TC) rose, and triacylglycerols (TG) fell in castrated rats, but were normalized by androgen substitution. VLDL components tended to be reduced, whereas HDL2 components rose following castration. In general, testosterone substitution normalized the alterations induced by castration. Adipose tissue LPL was higher in castrated rats than in control rats, whereas activities of HL and LCAT were not significantly affected by the treatments. Hepatic cholesterol concentration, and faecal excretion of cholesterol and bile acids were not significantly altered by the treatments. Considering all 3 groups together, there was a significant positive correlation between the concentration of plasma cholesterol and cholesterol in liver, between plasma HDL2-cholesteryl esters and hepatic cholesterol, and also between HL and faecal cholesterol excretion. The results suggest that short term castration of rats causes increased levels of lipoprotein lipase and thereby brings about a lowering of VLDL and an increased concentration of LDL and HDL2. These effects are reflected in hypotriacylglycerolaemia and hypercholesterolaemia.