Regulation of caltrin mRNA expression by androgens in the murine prostate

Testicular androgens induce the proliferation and differentiation of prosta tic epithelial cells by regulating the expression of androgen target genes. The use of subtractive hybridization to isolate genes that are differentia lly expressed during the early phase of androgen-induced prostatic regrowth in castrated mice resulted in identification of the murine caltrin gene. C altrin messenger RNA (mRNA) was highly expressed in the prostates of intact mice. Five weeks following castration of mice, steady state caltrin mRNA l evels were reduced by 70%. Within 12 hours of administration of pharmacolog ical doses of testosterone enanthate, steady state caltrin mRNA levels were elevated and increased to 90% of levels found in intact mice by 24 hours. Reverse transcriptase-polymerase chain reaction analysis of prostate tissue localized caltrin mRNA transcripts to the dorsal but not the ventral or la teral prostate. Within the dorsal prostate, in situ hybridization always lo calized caltrin mRNAs to the prostatic epithelial cells. Testosterone-induc ed increases in caltrin mRNA levels were detected prior to S-phase progress ion and initiation of proliferation in this cell population. Caltrin has be en demonstrated previously to function as a calcium transport inhibitor at the plasma membrane. Findings of this study indicate that caltrin is highly expressed and androgen-regulated in the murine prostate, where it is assoc iated with androgen-induced proliferation and differentiation of epithelial cells.