Effect of somatotropin on adipose tissue net glucose-stimulated lipogenesis in young goats

Net glucose-stimulated lipogenesis (NGSL: the rate of lipogenesis in the pr esence of glucose minus the rate of lipogenesis in the absence of glucose) in omental adipose tissue explants from young castrated male goats was eval uated in control animals (n = 3; placebo-treated) and in animals treated wi th the sustained release of recombinant bovine somatotropin (n = 4; bST; 10 0 mg at 7-day intervals in a 147 days lasting experiment). The rate of fatt y acid synthesis was determined in acute incubations in both freshly prepar ed and chronically cultured explants. Adipose explants remained metabolical ly active and retained their ability to respond to hormones when maintained in a tissue culture medium. NGSL in explants cultured for 24 h in the pres ence of insulin alone or bST alone, was non-significantly increased (more i n the controls) and decreased (more in bST-treated animals), respectively. However, cortisol alone decreased (P<0.05) NGSL in explants from both contr ol and bST-treated animals. In tissues from bST-treated animals, cortisol a cted synergistically with insulin to produce a higher rate of NGSL than tha t observed in cultures with insulin alone, bST inhibited insulin plus corti sol-stimulated lipogenesis significantly (P<0.05) in explants from bST-trea ted animals but non-significantly in control animals. The rates of NGSL wer e decreased (P<0.05) by catecholamines in explants from both control and bS T-treated animals. Norepinephrine (NE) and isoprenaline (ISO) were equally effective in the controls, whereas isoprenaline was more effective than nor epinephrine in bST-treated animals.