Abstract
Summary
Insulinase activity was determined by quantitating the degradation of insulin 131I substrate by rat liver homogenates. Plasma insulin was determined by a two-antibody radioimmunoassy procedure. In rats fasted for 1-4 days, insulin levels were 30% at 1 day and 10% at 4 days. Insulinase activity decreased less rapidly, being 80% at 1 day, 60% at 2 days, 35% at 3 days, and 25% at 4 days. On refeeding, insulin levels rose to normal promptly; whereas, insulinase activity did not return to normal until the third day. Refed animals treated with actinomycin D had only 48% of normal insulinase activity after 3 days of refeeding. Actinomycin D also inhibited the renewal of insulinase activity in insulin treated alloxan diabetic rats. These results are compatible with the hypothesis that insulin is an inducer of insulinase biosynthesis.
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