Responses of Plasma Apolipoproteins to Gonadectomy and Androgen Substitution in Male Rats

Summary

To obtain information on testosterone effects on plasma apolipoproteins, the amount and composition of apoproteins in lipoproteins of 5 density classes (VLDL, LDL, HDL_2b, HDL_2a, HDL₃) was estimated in 3 groups of adult male rats: normal control rats, castrated rats, and rats injected daily with testosterone propionate (200 μg/day) for one week after castration. Apoproteins were separated by sodium dodecylsulfate polyacrylamide gel electrophoresis after ultracentrifugation of plasma, and determined colorimetrically. Total amount of apoprotein carried in LDL (d = 1.006-1.063 g/ml) and HDL_2b (d = 1.063-1.100 g/ml) was higher in castrated than in control rats, but was not significantly different from controls in testosterone substituted rats. LDL apo B and HDL_2b apo E were higher in castrated than in normal rats; control levels were observed in androgen substituted rats. Except for a greatly increased relative amount of HDL_2b aPo E, and a decreased percentage of HDL_2b apo A-I in castrated rats, there were no significant alterations by castration of apoprotein composition of the lipoproteins. The results raise the question whether the androgenic state might affect processes related to the effects of plasma LDL apo B and HDL apo E.

Key-Words:

Apoproteins - Male Rats - Castration - Testosterone