[Characterization of the stimulant effect of 2 neuropeptides (thyroliberin (TRH) and vasoactive intestinal peptide (VIP)) on the secretion of the growth hormone in the rat].
The effects of thyrotropin-releasing hormone (TRH) and vasoactive intestinal peptide (VIP) on growth hormone (GH) secretion were investigated in vivo in freely moving, intact or mediobasal hypothalamic-lesioned rats and in vitro in incubation or superfusion systems of anterior pituitary tissue. In vivo, the two peptides induced a rapid increase of plasma GH levels in freely moving animals, bearing an extensive lesion of the mediobasal hypothalamus including the median eminence. VIP, but not TRH, was also effective in intact animals. In vitro, TRH and VIP stimulated GH release from incubated or superfused rat pituitaries in a concentrated manner: apparent affinity was 1.22.10(-8) M for TRH and 2.5.10(-9) M for VIP. These findings indicate that TRH and VIP exert a direct stimulatory action on somatotrophs, but that the effect of TRH (not observed in freely moving, intact rats) may be modulated by still other unidentified hypothalamic neurohormones.
D000818:Animals; D013006:Growth Hormone / Q000378:metabolism*; D007031:Hypothalamus / Q000502:physiology; D008297:Male; D008473:Median Eminence / Q000502:physiology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
D014660:Vasoactive Intestinal Peptide; D013973:Thyrotropin-Releasing Hormone; D013006:Growth Hormone
Caractérisation de l'effet stimulant de deux neuro-peptides (thyréolibérine-TRH et peptide vaso-actif intestinal-VIP) sur la sécrétion de l'hormone de croissance (GH) du rat.