Radioimmunoassay of plasma insulin in dogs and monkeys: application of the dextran-coated charcoal separation method.

The coated-charcoal separation method of Herbert (10) for radioimmunological determination of insulin in plasma of dogs and monkeys was evaluated by recovery, dilution, and reproducibility experiments. When optimal conditions were maintained, the method was well suited for plasma insulin-assay in these animals. In normal dogs and monkeys, fasting concentrations of plasma insulin ranged from less than 0.078 to 1.0 ng/ml. Intravenous infusion of xylitol, glucose or tolbutamide increased levels of plasma insulin three to 18 times over fasting levels in normal animals but not in two spontaneously diabetic dogs.