Effect of substance P/bombesin antagonists on the release of growth hormone by GHRP and GHRH.

Biochemical and biophysical research communications1991PMID: 1718273

Plain Language Summary

Substance P/bombesin antagonists selectively blocked the growth hormone release triggered by a growth hormone-releasing peptide (GHRP) but had minimal effect on GHRH-stimulated release, while a GHRH antagonist blocked only GHRH-stimulated release. This finding demonstrates that GHRP and GHRH stimulate growth hormone secretion through distinct pathways at the pituitary level.

Abstract

The substance P(SP)/bombesin (Bn) antagonists [DArg1DTrp7,9Leu11] SP(P-7482), [DArg1-DPro2DTrp7,9Leu11]SP (P-7483), [DArg1DPhe5DTrp7,9Leu11]SP(P-7492), and the growth hormone releasing hormone (GHRH) antagonist [DArg2Ala8,9,15]GHRH(1-29)(DC21-366) were tested for their in vitro effects on the release of growth hormone (GH) in the presence of GHRH and growth hormone releasing peptide, HisDTrpAlaTrpDPheLysNH2(GHRP). P-7492, P-7483, and P-7482 decreased, dose-dependently, the release of GH by GHRP (IC50 = 0.2 microM, 0.85 microM, and 6 microM, respectively). These antagonists had only a 10-15% inhibitory effect on the stimulated GH release of GHRH even at high dosage. DC21-366 decreased the stimulated release of GH by GHRH (IC50 = 0.16 microM) but not by GHRP. Neither SP nor Bn had GH releasing or inhibitory effects in this system.

Authors

Bitar, K G; Bowers, C Y; Coy, D H