Effects of somatostatin on plasma growth hormone and metabolite concentrations in fed and feed-deprived young female turkeys.

The sensitivity and magnitude of response to somatostatin-14 (SRIF-14) infusion in terms of changes in plasma concentrations of growth hormone (GH) and energy-related metabolites [nonesterified fatty acids (NEFA), glucose, and triacylglycerides (TG)] were determined in 9- to 11-wk-old fed or feed-deprived (FD; 20 h) female turkeys. The turkeys were sequentially infused with increasing doses of SRIF-14 (.0015 to 1.5 micrograms/min) concurrent with serial collection of blood samples (every 10 min). Plasma GH and NEFA concentrations were lower in fed than in FD birds. In fed birds only NEFA was minimally altered by SRIF-14 infusion. In FD birds, GH was decreased, but only at the highest dose of SRIF-14 (1.5 micrograms/min), whereas NEFA was decreased in a dose-dependent manner from .05 to 1.5 micrograms/min. Very rapid postinfusion rebounds of plasma GH and NEFA were observed in FD birds. Plasma glucose was not influenced by SRIF-14 in either fed or FD birds. Concentrations of plasma TG were depressed slightly by SRIF-14 in FD but not in fed birds. The present studies indicate that 1) FD birds are more sensitive to SRIF-14 infusion than are fed birds; 2) in FD birds, inhibition of lipolysis (indicated by plasma NEFA) is sensitive to lower dosages of SRIF-14 infusion than is inhibition of GH; and 3) SRIF-14 has little if any effect on TG and glucose metabolism.