DEVELOPMENTAL EXPRESSION AND ANDROGEN REGULATION OF 24 KDA SECRETORY PROTEINS BY THE MURINE EPIDIDYMIS

Two peptides with a molecular weight of 24 kDa and a P(i) of 8.4-8.8 w ere found to be synthesized and secreted specifically by the caput epi didymis of adult male mice under androgen control. The peptides can in teract with spermatozoa. In the present study, the developmental patte rn of [S-35]-methionine-labelled proteins synthesized by the murine ca put epididymis at 10, 20, 30 and 40 days of age were studied using two -dimensional polyacrylamide gel electrophoresis (2D PAGE) and autoradi ography. Active synthesis of the 24 kDa proteins was detected in the e pididymis from 20 days of age, but secretion of the two peptides was o nly observed from 30 days of age onwards. To determine whether androge ns influenced the active expression of 24 kDa proteins in the developi ng epididymis, their effect on [S-35]-methionine incorporation into pr oteins was assessed using 2D PAGE. Mice were either castrated, castrat ed then testosterone injected or simply testosterone injected at 10, 2 0, 30 or 40 days of age. Androgen control of 24 kDa protein expression was also studies in vitro in epididymal organ culture over a 10-day p eriod, with or without testosterone. Androgens were not involved in th e initiation of synthesis of the 24 kDa proteins from days 10 to 20, a s shown by in-vivo and in-vitro experiments. However, androgens appear ed to be essential for maintaining synthesis and secretion of the prot eins from 20 days of age onwards. Administration of excessive testoste rone was only able to increase secretion of the 24 kDa proteins in int act male mice aged 40 days.