Several aspects of glucose-U-C-14 metabolism were studied in the isolated perfused rat heart to compare the activities of nonsuppressible insulin-like activity (NSILA) and crystalline insulin. Like insulin, porcine NSILA prepared on a Dowex-50 column caused significant glucose disappearance and glycogen deposition. While 50 per cent of the insulin was cleared from the perfusate (immunoassay and bioassay) over sixty minutes, NSILA concentration, measured by the isolated fat cell bioassay, remained constant.
These results establish myocardium as a tissue on which NSILA has an action similar to insulin. Furthermore, these studies show an action of NSILA via a “normal” vascular tree and support the possibility that it may have a physiologic role. The lack of clearance of NSILA suggests that it may exert its insulin-like action over long intervals.