Lipolytic and diabetogenic effects of native and biosynthetic growth hormone in the chicken: a re-evaluation.

1. There is controversy as to whether growth hormone (GH) is lipolytic and/or diabetogenic in vivo in chickens. The ability of GH to influence circulating concentrations of free fatty acids was examined in anaesthetized (suppressing endogenous GH secretion) adult and young chickens using three preparations of GH. 2. Plasma concentrations of free fatty acids were increased following the intravenous injection of native bovine GH (50 micrograms/kg to either young or adult chickens), recombinant chicken GH (American Cyanamid) (50 micrograms/kg to adult chickens) and recombinant chicken GH (Amgen) (50 micrograms/kg to young chickens). 3. Similarly, infusion of recombinant chicken GH was accompanied by a gradual increase (P less than 0.05, 90 min following start of infusion) in plasma concentrations of free fatty acids in both anaesthetized hypophysectomized and sham operated young chickens. 4. These data support an acute lipolytic role for GH in the chicken. 5. The injection of neither bovine nor chicken GH had any consistent effect on circulating concentrations of glucose. Moreover, if GH was administered in the presence of glucose, GH had no effect on plasma concentrations of glucose. 6. Further evidence for a lack of a diabetogenic role for GH comes from the inability of chronic administration of GH to influence the decline in plasma concentrations of glucose following challenge with the insulin secretagogue, tolabutamide.