Effects of castration and maturational age of male rats on the process of copper-stimulated release of luteinizing hormone releasing hormone from median eminence explants: evidence that androgens increase the affinity of the copper-interactive sites for copper.

We have previously shown that chelated copper stimulates the release of luteinizing hormone releasing hormone (LHRH) from explants of the median eminence area (MEA) incubated under in vitro conditions and that this stimulation involves a ligand-specific interaction. In this study, we addressed the question: do testicular steroids regulate the secretory response of LHRH neurons to copper? MEA, obtained from immature, mature, immature castrated and sham-operated rats, were incubated in the presence of various concentrations of copper for 15 min and then in the absence of copper for an additional period of 30 min. We noted that after a lag period of 5 min of incubation, the rate of LHRH release increased in a linear fashion for a period of 15 min. In addition, the rate of LHRH release as well as the rate at which LHRH release was accelerated were saturable functions of the concentration of copper. When incubation was carried out in the presence of a nonsaturating concentration of copper (50 microM), the fractional amount (percent of the total MEA content) of LHRH released from the MEA of castrated rats was significantly (p less than 0.001) lower than that from sham-operated rats; stimulated release being 0.9% and 1.4%, respectively. Similarly, copper-stimulated release from the MEA of immature rats was lower than that from the MEA of mature rats. However, when incubation was carried out in the presence of saturating concentrations of copper (100 or 200 microM), the percentage of stimulated release from the MEA of castrated rats was similar to that of sham-operated rats and significantly lower than that of mature and sham-operated rats, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)