Time-dependent effects of increased serum prolactin levels on corticosterone synthesis and secretion in male rats.

To investigate the role of prolactin (PRL) on adrenal cortex function, male rats of the Wistar strain were rendered hyperprolactinemic by the grafting of one pituitary gland under the kidney capsule at 30 days of life. Age-matched animals were sham-operated to be used as controls. The well known increase of serum PRL levels, in grafted rats, observed in samples taken at 10 a.m. was only maintained at 2 a.m. on days 2, 4 and 14 after grafting, when compared to sham-operated rats. A differential time-dependent effects was observed for corticosterone (B) secretion. An increase in adrenal B content is observed during the whole period studied in grafted animals, as compared to sham-operated animals being statistically significant on days 2, 4, 14 and 40 days after the transplant operation. A biphasic pattern is described for serum B levels: whereas increased serum B levels were found on days 2 and 8 of the experimental period; a decrease in serum B levels were found in the chronic situation. The expected increase in adrenal weight was not sustained over the whole period studied being only increased on days 4, 8 and 30 after the grafting. All these data suggest that PRL exert a time-dependent modification in B secretion from the adrenal gland.