Effect of androgens on protein synthesis and secretion in various regions of the rat epididymis, as analysed by two-dimensional gel electrophoresis.

Protein synthesis and secretion has been quantified in three regions of the rat epididymis (initial segment, caput and cauda) by measuring the rate of incorporation of radioactive methionine by tissue pieces in vitro. The effect of androgens on protein synthesis and secretion was assessed by comparing tissue from untreated animals, castrated animals, and castrated animals receiving injections of testosterone propionate. Androgens caused up to a 2-fold increase in protein synthesis per unit wet weight of tissue. Qualitative effects of androgens on the types of proteins synthesized and secreted were assessed by two-dimensional gel electrophoresis. Androgens induced a differential response in the synthesis of secretory proteins in that some secretory proteins were androgen-regulated whereas others were not. Evidence was also obtained that protein synthesis and secretion in the initial segments of the epididymis responded to some local testicular factor in addition to androgen. The rate of decline in the synthesis of androgen-dependent secretory proteins following castration varied according to the protein. Moreover, the rate of decline in synthesis of the same protein varied markedly in different regions of the epididymis.