Prostatein C₃‐mRNA: A sensitive marker of androgen‐responsiveness in prostate explant cultures

Prostatein is an androgen‐dependent protein which is secreted by the rat ventral prostate. To determine if prostatein or its mRNA were responsive to androgen in vitro, prostate explants were cultured in media containing 0 or 25 nM dihydrotestosterone (DHT), estradiol (E₂), or cortisol (F). Prostatein concentrations in medium were measured by radioimmunoassay at 2 and 4 days and in homogenates at 4 days. They were not changed significantly by any of these steroids. The concentration of the mRNA for the C₃‐subunit of prostatein was determined by dot hybridization at 0, 2, 4, 6, and 8 days. It was decreased significantly by 2 days when compared with explants cultured in the presence of DHT and significant differences persisted through 8 days. In conclusion, quantitation of the mRNA for the C₃‐subunit of prostatein in short‐term cultures of ventral prostate explants appears to be more sensitive to changes in androgen concentration than does measurement of prostatein, per se. Prostatein C₃‐mRNA may be a useful marker for in vitro studies of androgen agonists and antagonists.