The effects of dexamethasone and growth hormone on hexokinase (HK) isoenzymes and glucose utilization were studied in adipose tissue from young rats. Dexamethasone (0.1 mg./kg. twice a day) caused hyperinsulinemia with normal blood glucose and marked diminution of adipose tissue HK-II after twenty-four and forty-eight hours. HK-I activity was reduced after twenty-four hours but normal after forty-eight hours. There was no change in HK four hours after a single injection of 0.2 mg./kg. Bovine growth hormone (1 mg. daily) had no effect after twenty-four hours, but increased HK-II after forty-eight hours. Plasma glucose and insulin remained unaltered by GH, and HK-I was also unchanged.
Isolated adipocytes showed the same changes as whole fat pads with dexamethasone, aging, fasting and refeeding; GH had no significant effect. HK-I activity under all circumstances was correlated with in vitro lipogenesis from glucose in the absence of insulin, but not with glucose oxidation. Both lipogenesis and oxidation in the presence of insulin (100 μU./1 ml.) werestrongly correlated with HK-II and glucose-6-phosphate dehydrogenase activįties. These results suggest that control of phosphorylation by HK-II may be a mechanism for mediating hormonal actions on insulin-stimulated glucose utilization.
