Effects of in vivo dihydrotestosterone treatment on changes in nocturnal surge of prolactin, luteal ultrastructure and P-450scc mRNA and protein content in pregnant rats.

We have demonstrated previously that the administration of dihydrotestosterone (DHT) decreases plasma progesterone levels within 24 h and thus, results in abortion during the first half of pregnancy (Am. J. Physiol. 241 (1981) E444-E448). The purpose of this study was to determine (a) if the administration of DHT suppresses plasma prolactin levels or its nocturnal surge within 24 h after the treatment, (b) how soon after the commencement of treatment do the concentrations of DHT increase and progesterone levels decrease in the circulation, (c) the ultrastructural changes that occur in corpora lutea, and (d) the changes in luteal P-450 side-chain cleavage (P-450scc) enzyme and mRNA content upon DHT treatment. Within 24 h after the commencement of DHT treatment, the nocturnal surge of prolactin, detected in both groups on day 10 at 03.30 h, was inhibited in DHT-treated rats as compared to controls. The non-surge levels of prolactin at 05.00 and 06.00 h were not different between groups. The intraovarian DHT pellet increased plasma levels of the steroid 3-fold within 2 h (blood samples were taken at 2-hourly intervals) when compared to controls. By 24 h DHT levels were decreased but were still higher than controls. Plasma progesterone levels began to fall 6 h after the commencement of treatment. Luteal tissue from animals treated with DHT appeared steroidogenic, and contained more lipid droplets than controls.(ABSTRACT TRUNCATED AT 250 WORDS)