Developmental expression and androgenic regulation of the mRNA for major secretory proteins of the rat epididymis.

The concentration of the mRNAs for two pairs of androgen-dependent secretory proteins of the rat epididymis has been measured by filter hybridization with cDNA during the course of post-natal development and following castration and androgen replacement of adult animals. The rate of synthesis of the secretory proteins, measured in an in vitro incubation system, was also ascertained during post-castration involution of the epididymis and during subsequent androgen replacement. The mRNAs for the proteins were first detected at 20 days of age and their levels increased rapidly to reach near adult levels between 30 and 40 days. In the caput epididymidis the levels of the mRNAs declined rapidly during the first week after castration and became undetectable by 16 weeks. Administration of testosterone propionate to animals castrated for 16 weeks reinduced the levels of mRNAs to maximum values by 1 week, but for one pair of proteins the reinduced maximum was only 30% of precastration values. This result, in conjunction with other information, is suggestive that this pair of proteins is under multihormonal control. In the cauda epididymidis, the kinetics of change in mRNA level during androgen withdrawal and replacement were slower than in the caput. In all instances, changes in the rate of synthesis of the secretory proteins followed by observed changes in their level of mRNA, suggesting an absence of androgenic control of translation in the epididymidis.