Gender-biased activity of the novel prolactin releasing peptides - Comparison with thyrotropin releasing hormone reveals only pharmacologic effects

The prolactin- (PRL) releasing activities of the newly described PRL-releas ing peptides (PrRPs) were compared to that of thyrotropin-releasing hormone (TRH) in dispersed, rat anterior pituitary cell cultures. A dose-related s timulation of PRL release by TRH was observed in cells harvested from both intact male and random cycle female pituitary donors. The minimum effective dose of TRH ranged from 1 to 10 nM, Neither PrRP-20 nor PrRP-31 significan tly altered PRL secretion in cells from male donors even at doses as high a s 1 CIM In cells harvested from females, only the highest doses of PrRP-20 and PrRP-31 tested (0.1 and 1.0 mu M) significantly stimulated PRL secretio n. The PRL-releasing action of TRH was observed already at 15 min of incuba tion, whereas those of PrRP-20 and PrRP-31 appeared only after 1 and 2 h of incubation, and the magnitude of PRL release in the presence of 1 mu M PrR Ps was significantly less than that of a similar dose of TRH, These data do not suggest a physiologically relevant role for the PrRPs in the neuroendo crine regulation of PRL secretion in intact male and nonlactating, random-c ycle female rats.