Transendothelial insulin transport is not saturable in vivo. No evidence for a receptor-mediated process.

In vitro, insulin transport across endothelial cells has been reported to be saturable, suggesting that the transport process is receptor mediated. In the present study, the transport of insulin across capillary endothelial cells was investigated in vivo. Euglycemic glucose clamps were performed in anesthetized dogs (n = 16) in which insulin was infused to achieve concentrations in the physiological range (1.0 mU/kg per min + 5 mU/kg priming...