Growth hormone (GH) responses to arginine and L-dopa alone and after GHRH pretreatment.
In order to investigate the mechanisms by which arginine and L-dopa cause GH release in humans we measured the GH response to GHRH 1-44 (200 micrograms i.v.), arginine (30 g i.v. over 30 min) and L-dopa (500 mg orally) administered alone and 120 minutes following pretreatment with GHRH 1-44 (200 micrograms i.v.) in normal male subjects. Prior GHRH administration abolished the GH response to subsequent GHRH. Arginine infusion induced a rise in GH levels maximal at 45 min. Following GHRH pretreatment the GH response to arginine was enhanced, with peak values of 19.3 +/- 6.4 vs 53.3 +/- 16.5 mU/l (mean +/- SEM) respectively (P less than 0.02). L-dopa alone induced a rise in GH levels maximal at 90 min (17.6 +/- 7.4 mU/l, mean +/- SEM) but this rise was abolished by pretreatment with GHRH.
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Department of Medicine, University of Wales College of Medicine, Health Park, Cardiff, UK.
Dieguez
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Valcavi
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Edwards
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Hall
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Scanlon
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MF
D000328:Adult; D001120:Arginine / Q000494:pharmacology*; D004357:Drug Synergism; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D006801:Humans; D007980:Levodopa / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008297:Male; D011388:Prolactin / Q000097:blood
D007980:Levodopa; D011388:Prolactin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D001120:Arginine