CHANGES IN LEVELS OF 'ATYPICAL' CIRCULATING INSULIN AFTER INFUSING 'TYPICAL' INSULIN THROUGH THE LIVER

Abstract

SUMMARY: Insulin was infused into the portal vein of four greyhounds previously pancreatectomized; assays on their hepatic venous serum showed thereafter not only a striking rise in total insulin-like activity (ILA), but also a steady rise in 'atypical' ILA (to 200–300% of the pre-infusion level). For controls in two other pancreatectomized greyhounds, with their livers temporarily excluded from the circulation, insulin was similarly infused into a femoral vein and the brachial vein sampled for assays; no rise in 'atypical' ILA was then seen. The levels of 'typical' or 'atypical' ILA in the three venous samples were not found to be altered by oxygenation before their plasmas were separated for bioassay. These experiments suggest that 'atypical' insulin is found in serum because some of the 'typical' insulin secreted by the pancreas is transformed to the 'atypical' form during its passage through the liver.