Involvement of pituitary adenylate cyclase-activating polypeptide in growth hormone secretion induced by serotoninergic mechanisms in the rat.
Pituitary adenylate cyclase-activating polypeptide-38 (PACAP-38) stimulated GH secretion in superfused rat anterior pituitary cell in vitro and in conscious male rats in vivo. PACAP-38-induced GH secretion was inhibited by PACAP-(6-38), an N-terminal-deleted analog, at 100-fold concentrations of PACAP-38 both in vitro and in vivo. In contrast, a GH-releasing hormone antagonist did not affect the action of PACAP-38 to stimulate GH release in vitro. Plasma GH increase induced by i.v. injection of 5-hydroxy-L-tryptophan (1 mg/100 g BW), a precursor of serotonin, was blunted by PACAP-(6-38) (1 nmol/100 g BW, i.v.), whereas spontaneous pulsatile GH secretion in conscious male rats, which is governed by hypothalamic GH-releasing hormone and somatostatin, was not affected by repeated i.v. injection of PACAP-(6-36). These findings suggest that PACAP-(6-38) is a potent antagonist of PACAP-38 to stimulate GH secretion both in vivo and in vitro. Taken together with the facts that PACAP-38 is highly concentrated in the hypothalamus and that is released into the hypophysial portal blood, our present findings suggest that PACAP-38 might play a stimulatory role on GH secretion induced by serotoninergic mechanisms in the rat.
Yamauchi
K
K
Department of Medicine, Shimane Medical University, Izumo, Japan.
Murakami
Y
Y
Koshimura
K
K
Nishiki
M
M
Tanaka
J
J
Kato
Y
Y
D006916:5-Hydroxytryptophan / Q000494:pharmacology; D000818:Animals; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000037:antagonists & inhibitors / Q000494:pharmacology; D007031:Hypothalamus / Q000378:metabolism; D008297:Male; D009479:Neuropeptides / Q000378:metabolism / Q000494:pharmacology*; D018377:Neurotransmitter Agents / Q000378:metabolism / Q000494:pharmacology*; D010507:Periodicity; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000502:physiology*
C495403:Adcyap1 protein, rat; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012701:Serotonin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D006916:5-Hydroxytryptophan