Plasma lipoprotein responses to castration and androgen substitution in rats

To elucidate plasma testosterone/lipoprotein relationships in a controlled animal experiment, whole-plasma lipid concentration and amount of lipoprotein components in five density classes were determined in three groups of rats: normal control rats, short-term castrated rats, and rats treated with testosterone propionate after castration. Compared to control rats, whole-plasma total cholesterol, free cholesterol (FC), cholesteryl-ester (CE), and phospholipids (PL) rose in castrated rats but were normalized in rats receiving androgen substitution. There were no group differences in whole-plasma triacylglycerol concentration. The levels of protein, FC, and CE in LDL (d = 1.006 to 1.063 g/mL) and HDL2b (d = 1.063 to 1.100 g/mL) of castrated rats were appreciably higher than in LDL and HDL2b of control rats. In androgen-substituted rats the level of LDL and HDL2b protein, FC, CE, and PL were all reduced to normal or subnormal levels. The esterified fraction of cholesterol in whole plasma was increased by androgen treatment. There were no significant group differences in VLDL (d less than 1.006 g/mL), HDL2a (d = 1.100 to 1.125 g/mL) or in HDL3 (d = 1.125 to 1.210 g/mL). The results suggest that short-term castration of rats is followed by hyperlipoproteinemia due to lack of testosterone and that the lipoprotein changes mainly reside in LDL and the less-dense type of HDL.