Abstract
A comparison of the processes controlling the increase in hepatic malic enzyme activity in insulin-treated normal and diabetic rats indicated the existence of two distinct regulatory mechanisms. Livers were removed at 12, 36, and 60 h after insulin treatment of normal and alloxan-diabetic rats, and the activity, quantity, and specific activity (units/nmol), of malic enzyme was determined. In normal rats, a significant increase in activity occurred 12 h after insulin, whereas 36 h of insulin treatment was required for diabetic rats to show an increase in enzyme activity. This suggested that the return of malic enzyme activity from the depleted levels measured in diabetic rats probably involved a different sequence of events. A malic enzyme specific radioimmunoassay confirmed this. The increase in activity in insulin-treated normal rats was due to an increase in the quantity of malic enzyme. In insulin-treated diabetic rats, the increase in activity resulted from increases in both enzyme quantity and the specific activity of the enzyme, which returned to levels observed in normal rats.
Highlights
A comparison of theprocessescontrolling the in- In the current study, the kinetics of the increase in the crease inhepaticmalicenzyme activity in insulin- quantity and specific activity of malic enzyme following intreated normal and diabetic rats indicated the exist- sulin treatment of diabetic rats was correlated with the inence of two distinct regulatorymechanisms
Normal rats gained 6.42 -+ 1.0 g/day with plasma glucose levels of 141 k 16 mgldl.the diabetic rats clearly satisfied the criteria for experimental diabetes of little or no increase in body weight and plasma glucose levelsin excess of 300 mg/dl
Several important differences were evident in the kinetics and magnitude of the increase in hepatic malic enzymeactivity in insulin-treated normal and diabetic rats (Fig. 1).A statistically significant increase in totalactivity was observed in normal rats 12 h after the initiation of diet and insulin treatment
Summary
A comparison of theprocessescontrolling the in- In the current study, the kinetics of the increase in the crease inhepaticmalicenzyme activity in insulin- quantity and specific activity of malic enzyme following intreated normal and diabetic rats indicated the exist- sulin treatment of diabetic rats was correlated with the inence of two distinct regulatorymechanisms. The increasein activity in insulin-treatednormal rats was due to an increase in the quantity of malic enzyme. Several important differences were evident in the kinetics and magnitude of the increase in hepatic malic enzymeactivity in insulin-treated normal and diabetic rats (Fig. 1).A statistically significant increase in totalactivity was observed in normal rats 12 h after the initiation of diet and insulin treatment.
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