A comparative study of hormonal regulation of three secretory proteins (prostatic secretory protein-PSP94, probasin, and seminal vesicle secretion II) in rat lateral prostate

The rat dorsolateral prostate secretes several major known proteins, althou gh their physiological and reproductive functions are largely undefined. In the present study we examined and compared the in vivo hormonal regulation of the messenger RNA (mRNA) expression of three major secretory proteins, including prostatic secretory protein of 94 amino acids (PSP94 or beta -mic roseminoprotein), probasin, and seminal vesicle secretion II(SVSII), in lon g-term castrated lateral prostates (LP) by in situ hybridization and semiqu antitative RT-PCR. The protein levels of PSP94 in the castrated LPs were al so examined by Western blotting. PSP94 is a small protein newly isolated fr om the rat prostate gland and demonstrates highly specific expression in th e LP. The results of in situ hybridization showed that PSP94, probasin, and SVSII were highly expressed in the intact LP. The hybridization signals of probasin and PSP94 disappeared in the 60-day postcastrated LPs, whereas th e signals of SVSII dropped sharply in the 14-day postcastrated LPs. Similar patterns of decreasing mRNA levels of the three proteins in the castrated LPs were observed by RT-PCR analysis. Their mRNA transcripts were restored to normal levels after replacement with testosterone. The results indicate that these secretory proteins are all under androgen regulation in the rat LP. Interestingly, we also observed that their degrees of sensitivity or re sponsiveness to androgen withdrawal are different. Their mRNA levels droppe d in response to duration of castration in the following decreasing order: SVSII, PSP94, and probasin. Besides androgen [dihydrotestosterone (DHT)], w e also examined the effects of glucocorticoid [dexamethasone (DEX)], proges tin [medroxyprogesterone acetate (MPA)], and zinc on their gene expressions in castrated LPs. We observed that the mRNA transcripts of both PSP94 and probasin were increased after treatments with DHT, DEX, and MPA, suggesting that these two proteins could also be regulated by glucocorticoid and prog estin. In contrast with probasin, PSP94 and SVSII were not induced by ZnSO4 treatment. On the other hand, SVSII expression was only increased signific antly by DHT and moderately by MPA, but not by DEX, suggesting that SVSII i s under strict control by androgen.