Studies Employing a New Method for the Recovery of Biologically Active Insulin from Acid Alcoholic Extracts of Pancreas and Blood Serum

Abstract

A dialysis method for the preparation of physiologic insulin solutions is described. The insulin potency of these solutions was determined by the mouse hemidiaphragm four-point-parallel-slope assay. When very high precision tests were necessary, the Wardlaw-Moloney procedure was used. The precipitate formed in the dialysis bag when pancreatic extracts were used had an antagonistic or inhibiting effect on insulin activity. The concentration of extractable insulin in the pancreas of immature guinea pigs was significantly less than in the pancreas of heavier, mature guinea pigs. The concentration of extractable insulin in the islet tissue of guinea pigs was very much less than in the islet tissue of the rat. Guinea pig antibeef insulin antibody failed to neutralize guinea pig insulin extracted from pancreas or from serum. In the rat the reduction in insulin content of pancreas with starvation is confirmed, but no significant reduction in pancreatic insulin was found in the starved guinea pig. Applying these procedures to serum it was found (1) that a suspension of the precipitate in the supernatant yields an insulin activity of as high as 7 mU per milliliter serum, (2) that the washed precipitate has insulin activity, (3) that the supernatant solution usually yields several mU insulin per milliliter serum.