Abstract
When rat adipose tissue was incubated with 270μU insulin, its stimulatory action on glucose metabolism appeared one hour after the start of the incubation, while an inhibitory action of cortisol on glucose metabolism was demonstrated as late as 2hrs. after its addition to the medium. When fat pads were incubated with cortisol and insulin, the latter action persisted without any suppression by cortisol.
When the tissue was preincubated with cortisol for more than 30 min, however, the stimulatory action of insulin which was subsequently added to the medium was substantially decreased. Thus, the longer the preincubation of the adipose tissue with cortisol was, the more greatly cortisol antagonized insulin action. An inhibitory action of cortisol on glucose metabolism was clearly demonstrated in adipose tissues treated with trypsin under conditions where the stimulatory action of insulin was abolished. When epinephrin 10-5M, which itself showed an inhibitory action on uptake of glucose by adipose cells, was added to the incubation medium concomitantly with cortisol 10-5M, there was seen a synergism between inhibitory actions of both hormones.These data may indicate that the antagonism between cortisol and insulin is not based upon a competition for a receptor on the adipose cell membrane but upon their interaction at a site in the adenyl cyclase system of homone action.
