Antagonism of glucocorticoid action by insulin

Glucocorticoids are known to have profound effects on glucose and protein metabolism as a result of their ability to regulate metabolic processes in various tissues of the adult. In addition to these effects in the adult, glucocorticoids have been implicated as important regulators in the development of several different tissues (1-5). In a number of these systems shown to be glucocorticoid sensitive it has been found that insulin augments the response. In the liver, both hormones are required to enhance glycogen synthetase activity resulting in an increased deposition of glycogen (6). Differentiation of mammary epithelial cells in vitro and the subsequent synthesis of casein and a-lactalbumin have been shown to be dependent on the simultaneous presence of insulin, glucocorticoids and prolactin (4,7). Insulin and glucocorticoids have also been shown to act synergistically in the induction of glutamine synthetase in 3T3-L1 adipocytes (8) and of tyrosine aminotrans-ferase in HTC cells (9,10)