COMPARISON OF AN IMMUNOASSAY AND BIOASSAY OF INSULIN IN SHEEP PLASMA

Abstract

SUMMARY Insulin concentrations were determined in sheep plasma using a radio-immunoassay and a bioassay (rat epididymal fat pad) technique. Both methods indicate an increase in plasma insulin after intravenous injection of insulin or glucose into sheep, followed by a decline as glucose levels return to normal. With both methods, plasma levels before injection are comparable with values reported for human plasma. However, the response of the fat pad to sheep plasma was fully inhibited by anti-insulin serum; acid ethanol extraction did not increase the apparent level of insulin; the concentrations indicated by the fat-pad method correspond with values that have been obtained with the diaphragm assay. No evidence has been found for a bound form of insulin in sheep plasma. There was no potentiation by sheep plasma of the response of the fat pad to crystalline insulin.