Effect of gastrin-releasing peptide (GRP) and GRP antagonists on TSH secretion from rat isolated pituitaries.
It has previously been demonstrated that gastrin releasing peptide (GRP), a bombesin-like peptide, inhibited TSH release "in vivo". In this study, we have shown that GRP acts directly at the pituitary gland, inhibiting basal and TRH-stimulated TSH release from incubated rat anterior pituitary glands. This effect was observed at the highest GRP concentration (10(-5) M), but not at the lower concentrations (10(-7) and 10(-9) M). Incubation of the glands with two antagonists of GRP (d-Phe8-GRP and Gly6-GRP) induced an increase of basal TSH secretion. We suggest a physiological role of locally produced bombesin-like peptides in the control of TSH release. Another antagonist (Ala6-GRP) did not change TSH secretion. This result suggests the existence of different subtypes of GRP receptors in the anterior pituitary gland.
Santos
C V
CV
Department of Physiological Sciences, State University of Rio de Janeiro, Brazil.
Pazos-Moura
C C
CC
Moura
E G
EG
D000818:Animals; D019886:Gastrin-Releasing Peptide; D008297:Male; D010455:Peptides / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012636:Secretory Rate / Q000187:drug effects; D013972:Thyrotropin / Q000378:metabolism*
D010455:Peptides; D019886:Gastrin-Releasing Peptide; D013972:Thyrotropin