Antagonism of insulin action in cultured pig adipose tissue by pituitary and recombinant porcine growth hormone: potentiation by hydrocortisone.

The effects of physiological levels of pituitary porcine GH (ppGH) and recombinant pGH (rpGH) on lipogenesis in pig adipose tissue incubated with insulin and hydrocortisone (HC) were measured in short term (2-h) incubations and after long term culture (50 h). HC (50 ng/ml) had no effect on lipogenesis in 2-h incubations; however, HC and insulin (10 ng/ml) maintained the lipogenic capacity of cultured tissue at rates comparable to those in fresh adipose tissue. Neither ppGH nor rpGH (1 and 10 ng/ml, respectively) had any effect in short term incubations. After 50 h of culture, ppGH and rpGH both directly antagonized the ability of insulin to maintain lipogenesis; however, this antagonism was markedly enhanced by HC. The present study is the first to demonstrate a direct antagonism of insulin action by ppGH and rpGH in pig adipose tissue, and a marked potentiation of this antagonism by HC. This intrinsic property of pGH may account, in part, for the decrease in adipose tissue growth rates in pigs treated chronically with pGH.