The effect of GHRH on TSH release in rats in vivo and in vitro.
In man, GHRH has been shown to potentiate the TSH-releasing activity of TRH. To study the way by which GHRH affects TRH-stimulated TSH release, we examined the effect of GHRH (1-29)NH2 on basal and stimulated TSH secretion in intact male rats and superfused dispersed rat pituitary cells. In the intact rats, GHRH(1-29)NH2 potentiated TRH-stimulated TSH release in the evening, but potentiation was not observed in the morning and in dispersed pituitary cells. Basal TSH levels were not changed by GHRH(1-29)NH2. It is concluded that GHRH(1-29)NH2 potentiates the TSH-releasing activity of TRH in the evening in rats possibly through suprahypophyseal disinhibition.
Looij
B J
BJ
Department of Endocrinology, University Hospital, Leiden, The Netherlands.
Nieuwenhuijzen Kruseman
A C
AC
Roelfsema
F
F
van der Heide
D
D
Hoogma
R P
RP
Schröder-van der Elst
J P
JP
D000818:Animals; D004357:Drug Synergism; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013972:Thyrotropin / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D013007:Growth Hormone-Releasing Hormone