title: Effects of phenylalanine, histidine, and leucine on basal and GHRH-stimulated GH secretion and on PRL, insulin, and glucose levels in short children. Comparison with the effects of arginine.
abstract: Of the amino acids arginine is the most potent GH secretagogue in man. It potentiates the GH response to GHRH, exerts a weaker PRL-releasing effect, stimulates insulin and glucagon and induces a biphasic glucose variation. The potency and effects of other amino acids on pituitary and pancreatic hormones need to be clarified. In 43 children with normal short stature (5.3-14.0 yr; 30 M and 13 F) the effects of the infusion of phenylalanine (Phe, 0.08 g/kg), histidine (His, 0.1 g/kg), and leucine (Leu, 0.08 g/kg) on basal and GHRH-stimulated GH secretion and on PRL, insulin and glucose levels were studied and compared with those of arginine at high (hArg, 0.5 g/kg) or low dose (lArg, 0.2 g/kg). Phe increased basal (p < 0.05) but not GHRH-stimulated GH levels, induced PRL and insulin rises (p < 0.03 and p < 0.03), and did not change glycemia. Though a trend toward an increase in basal GH levels was found after His, His and Leu did not significantly modify either basal or GHRH-induced GH secretion nor basal PRL, insulin and glucose levels. Both hArg and lArg increased basal (p < 0.0001 and p < 0.05, respectively) and GHRH-stimulated GH levels (p < 0.006 and p < 0.006). hArg increased both PRL (p < 0.002) and insulin levels (p < 0.005) more (p < 0.0005 and p < 0.004) than lArg (p < 0.005 and p < 0.005), while glucose levels showed a similar increase followed by a similar decrease. We conclude that in childhood: a) Phe significantly increases GH secretion but, differently from Arg, does not potentiate the response to GHRH, suggesting different mechanisms of action of these amino acids; b) differently from His and Leu, Phe is a PRL and insulin secretagogue but is less potent than Arg; c) Arg has the highest stimulatory effect on pituitary and pancreatic hormones.
authors.affiliation: Department of Internal Medicine, University of Turin, Italy.
authors.forename: J
authors.initials: J
authors.lastname: Bellone
authors.forename: M R
authors.initials: MR
authors.lastname: Valetto
authors.forename: G
authors.initials: G
authors.lastname: Aimaretti
authors.forename: M
authors.initials: M
authors.lastname: Segni
authors.forename: C
authors.initials: C
authors.lastname: Volta
authors.forename: G
authors.initials: G
authors.lastname: Cardimale
authors.forename: C
authors.initials: C
authors.lastname: Baffoni
authors.forename: A M
authors.initials: AM
authors.lastname: Pasquino
authors.forename: S
authors.initials: S
authors.lastname: Bernasconi
authors.forename: E
authors.initials: E
authors.lastname: Bartolotta
authors.forename: M
authors.initials: M
authors.lastname: Mucci
authors.forename: E
authors.initials: E
authors.lastname: Ghigo
mesh_terms: D000293:Adolescent; D001120:Arginine / Q000009:adverse effects / Q000494:pharmacology*; D001786:Blood Glucose / Q000378:metabolism; D001827:Body Height; D002648:Child; D002675:Child, Preschool; D004357:Drug Synergism; D005260:Female; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D006639:Histidine / Q000009:adverse effects / Q000494:pharmacology*; D019382:Human Growth Hormone / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000097:blood; D007930:Leucine / Q000009:adverse effects / Q000494:pharmacology*; D008297:Male; D010649:Phenylalanine / Q000009:adverse effects / Q000494:pharmacology*; D011388:Prolactin / Q000097:blood; D011627:Puberty
chemical_list: D001786:Blood Glucose; D007328:Insulin; D019382:Human Growth Hormone; D010649:Phenylalanine; D006639:Histidine; D011388:Prolactin; D013007:Growth Hormone-Releasing Hormone; D001120:Arginine; D007930:Leucine