THE INFLUENCE OF AMINO ACIDS AND SOMATOSTATIN ON PROLACTIN AND GROWTH HORMONE RELEASE IN MAN

Abstract

The effect of an i.v. load of individual amino acids (alanine, arginine, histidine, leucine, phenylalanine and valine) on serum prolactin (Prl) and growth hormone (GH) concentrations was studied in healthy adult males (n = 5). A rise in Prl and GH with a maximal increment of 15.9 .+-. 6.7 (SE) ng/ml, and 12.4 .+-. 4.9 ng/ml above basal levels, respectively, (P < 0.05) was observed after i.v. arginine. Following i.v. phenylalanine the mean peak level of Prl rose from 9.9 .+-. 3.5 to 29.9 .+-. 7.3 ng/ml (P < 0.01), whereas GH concentration remained unchanged. I.v. leucine induced an immediate rise in GH, but not in serum Prl. Serum concentrations of Prl and GH failed to increase upon the infusion of either alanine or histidine or valine. Additional somatostatin administration starting prior to amino acid infusion diminished the amino acid induced increase of Prl and GH release.