Enhanced vesicular ingestion of nonenzymatically glucosylated proteins by capillary endothelium.

Isolated capillary endothelial cells exhibit an enhanced vesicular ingestion of nonenzymatically glucosylated myoglobin and ovalbumin. Proteins were incubated in the presence of glucose and the extent of nonenzymatic glucosylation was assessed using NaB3H4 reduction. Unmodified and glucosylated proteins were fluorescently labeled, and vesicular ingestion was quantified using a system of isolated capillary endothelium. Glucosylated myoglobin exhibited a 3.5-fold greater rate of vesicular injection as compared to unmodified myoglobin during the initial 30 min of ingestion. Glucosylated ovalbumin was vesicularly ingested at a rate 15-fold greater than the rate observed for unmodified ovalbumin during the initial 30 min of ingestion. These results indicate that glucosylation of small proteins may alter their subsequent recognition by the endothelial cell plasma membrane and result in increased sequestration within micropinocytic vesicles.