Effect of substance P/bombesin antagonists on the release of growth hormone by GHRP and GHRH. |
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| Authors: | K G Bitar C Y Bowers D H Coy |
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| Institution: | Department of Medicine, Tulane University School of Medicine, New Orleans, LA 70112. |
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| 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. |
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