Expression of cystatin-related protein and of the C3-component of prostatic-binding protein during postnatal development in the rat ventral prostate and lacrimal gland.

The expression of cystatin-related protein (CRP) and of the C3-component of prostatic-binding protein (PBP) during postnatal development of the rat was studied by Northern blotting, dot blot and in situ hybridisation, and by radioimmunoassay or immunoblotting. In intact male rats, very little or no PBP-C3 could be detected in the prostate at 10 days, but at 20 days there was already strong expression. By in situ hybridisation, the first expression of C3 mRNA was observed at 13 days in the prostate and at 22 days in the lacrimal gland. For CRP, this occurred at 16 and 22 days, respectively. Neither CRP nor C3 was expressed in prepubertal male rats castrated at day 1 or day 10 or in female rats. Androgen treatment of intact male animals did not advance the expression of both mRNAs in the prostate, but did so in the lacrimal gland with first expression of C3 at 19 instead of 22 days and of CRP at 13 instead of 22 days. Identical values were obtained in female rats. Androgen treatment of castrated adult male rats resulted in a more rapid and homogeneous secondary induction. Positive immunostaining for the androgen receptor (AR) was observed in the lacrimal gland at 7 days, but its concentration, estimated by immunoblotting, was still low at 10 days. Maximal levels, reached at 30 days, were markedly higher in male than in female rats. In conclusion, CRP and C3 are induced by androgens in prepubertal rats. The time point of induction, however, is probably determined by other tissue and differentiation-dependent factors in addition to androgens and the AR.