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SOMATOSTATIN‐28 AND SOMATOSTATIN‐14 SUPPRESSION OF ARGININE‐, INSULIN‐, AND TRH‐STIMULATED GH AND PRL SECRETION IN MAN
Author(s) -
MILLAR R. P.,
KLAFF L. J.,
BARRON J. L.,
LEVITT N. S.,
LING N.
Publication year - 1983
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/j.1365-2265.1983.tb03212.x
Subject(s) - medicine , endocrinology , somatostatin , arginine , median eminence , stimulation , insulin , prolactin , chemistry , secretion , hypothalamus , hormone , amino acid , biochemistry
SUMMARY GH and PRL responses to arginine infusion and to the combined pituitary stimulation test (0·1 u/kg of insulin, 200 μg of TRH, 100 μg of LHRH) were compared in five normal men during infusions of somatostatin‐14 (SS‐14) and somatostatin‐28 (SS‐28), and during control infusions of vehicle alone. SS‐14 and SS‐28 were infused at a rate of 1·8 nmol/kg over 210 min. Arginine (0·5 g/kg) was infused from 30 to 60 min and the combined pituitary stimulation test commenced at 120 min. Arginine (0·5 g/kg) infused from 30 to 60 min induced an increase in GH secretion in all subjects and this increase was completely abolished in these same subjects when infused with SS‐14 and SS‐28. Arginine‐induced hyperglycaemia was significantly greater during infusion of SS‐14 and further enhanced by infusion of SS‐28. A small increase in PRL secretion occurred after arginine infusion and this was not inhibited by SS‐14 or SS‐28. Insulin and TRH administration induced marked increases in both GH and PRL secretion. The mean GH increase was significantly inhibited by SS‐14 and SS‐28 up to 165 min but not thereafter. The PRL increase was significantly inhibited by SS‐28 but not by SS‐14 and this greater efficacy was also indicated by administering different doses of SS‐28 to one subject. Taken together with the demonstration that SS‐28 is released from the median eminence, these findings indicate that SS‐28 has a hormonal role in the regulation of GH and PRL secretion.