Insulin and dexamethasone effects on liver fructose bisphosphatase

Insuling perfusion of isolated diabetic rabbit liver and glucocorticoid perfusion of isolated normal rabbit liver resulted in an increased accumulation of immunoreactive fructose bisphosphatase (nmol/g). The insulin effect was maximal at 30 min with concentration (nmol/g) and specific activity (units/nmol) returning to normal within 2 h after insulin removal. Similarly, dexamethasone perfusion increased enzyme concentration and decreased its specific activity; however, the effects were maximal at 60-120 min. The results parallel those previously demonstrated in whole animals and establish that both hormones influence the enzyme by direct effects on the liver.