Effects of glucagon infusion, alone or in combination with somatostatin, on plasma growth hormone and metabolite levels in young female turkeys under different feeding regimens.

The lipolytic effect of glucagon alone or in combination with somatostatin-14 (SRIF-14) was studied in 9- to 11-wk-old female turkeys that either consumed feed ad libitum or were deprived of feed (FD) for 20 h. During the infusion of various doses of glucagon (.005 to 1.5 micrograms glucagon/min), blood samples were serially collected every 10 min for determination of plasma concentrations of growth hormone (GH) and energy-related metabolites [nonesterified fatty acids (NEFA), glucose, and triacylglycerol (TG)]. Glucagon infusion resulted in decreases (P < .05) in plasma GH in both groups of turkeys. During glucagon infusion, dose-dependent increases in both glucose and NEFA occurred, with greater relative increases in the ad libitum turkeys. In contrast, plasma TG was decreased by glucagon infusion in the ad libitum turkeys but unchanged in the FD turkeys. The effect of simultaneous infusion of SRIF-14 and glucagon on GH and NEFA concentrations varied depending on the previous hormonal treatment. Plasma glucose was not affected by SRIF-14 in either group of turkeys. The present studies show that: 1) glucagon is an important agent for directing carbohydrate and lipid metabolism in growing female turkeys; 2) SRIF-14 has little effect on carbohydrate metabolism, but does affect lipolysis in a complex manner with glucagon; and 3) in vivo, glucagon depresses plasma GH.