title: Prolactin-releasing Peptide (PrRP) increases prolactin responses to TRH in vitro and in vivo.
abstract: The Prolactin-releasing Peptide (PrRP) is a 31-aminoacid peptide produced and secreted from the hypothalamus, and postulated to promote the prolactin release from the pituitary. However, the action of PrRP remain controversial, since it was described to have potency comparable enough to TRH, although there are many evidences that PrRP is less potent than TRH. Here we have studied the effects of PrRP alone or in combination with TRH in the prolactin levels of rat pituitary primary cell cultures in vitro and also in vivo prolactin responses in randomly cycling and estrogens-treated female rats. PrRP itself increased prolactin levels in vitro and in vivo, although in a magnitude several times lower than TRH. In vivo PrRP promotes an atypical non-peaking progressive and maintained prolactin increase. On the other hand, PrRP markedly increased the prolactin responses to TRH in vitro (10-30 fold increase) and in vivo (up to three-fold increase). In addition, FGF-2 and EGF, two important growth factors present in the pituitary, reduced the PrRP-induced prolactin increase in vitro. Taken together our results suggest that PrRP released from the hypothalamus may be relevant to modulate the circulating prolactin levels in the rat.
authors.affiliation: Department of Functional Biology and Health Sciences, Laboratory of Endocrinology, Faculty of Sciences, Campus of Vigo, University of Vigo, Vigo, 36310, Spain. carlos.spuch@gmail.com
authors.forename: Carlos
authors.initials: C
authors.lastname: Spuch
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Diz-Chaves
authors.forename: Diego
authors.initials: D
authors.lastname: Pérez-Tilve
authors.forename: Mayte
authors.initials: M
authors.lastname: Alvarez-Crespo
authors.forename: Federico
authors.initials: F
authors.lastname: Mallo
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004357:Drug Synergism; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D007028:Hypothalamic Hormones / Q000494:pharmacology*; D009479:Neuropeptides / Q000494:pharmacology*; D011388:Prolactin / Q000378:metabolism*; D056690:Prolactin-Releasing Hormone; D051381:Rats; D017207:Rats, Sprague-Dawley; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
chemical_list: D004338:Drug Combinations; D007028:Hypothalamic Hormones; D009479:Neuropeptides; C534379:Prlh protein, rat; D056690:Prolactin-Releasing Hormone; D016222:Fibroblast Growth Factor 2; D013973:Thyrotropin-Releasing Hormone; D004815:Epidermal Growth Factor; D011388:Prolactin