title: Intracellular pathways of insulin transport across vascular endothelial cells.
abstract: Processing and transport of hormones across vascular endothelial cells may modulate hormone action at subendothelial tissue sites. Insulin was transported across cultured rat capillary and bovine aortic endothelial cells, after a delay of 5-10 min, at a constant rate for 60 min at 37 degrees C. 125I-labeled insulin transport was inhibited by 88 +/- 11% (SE, n = 4) and 75 +/- 18% (SE, n = 4) in the presence of anti-insulin receptor antibody and unlabeled insulin (at 10(-7) M), respectively. Reverse phase high-performance liquid chromatography showed 88% of the 125I-insulin transported over 60 min was indistinguishable from the 125I-insulin added to the cells at 4 degrees C. In aortic endothelial cells preincubated with 2.3 x 10(-9) M of insulin for 24 h, insulin receptor binding was downregulated by 67%, and 125I-insulin transport was decreased by 52 +/- 11%. The proton ionophore monensin (0.05 mM) increased the internalized insulin in bovine aortic endothelial cells by 78%, with a corresponding decrease in 125I-insulin released by 76 +/- 2% (SE, n = 4). 125I-insulin transport across the aortic endothelial cell monolayer was similarly decreased (54 +/- 12%, SE, n = 4) by monensin. In contrast, the lysosomal protease inhibitor leupeptin had no effect. Degradation and transport were similarly dissociated by low temperature. At 15 degrees C, no significant insulin degradation was detected, whereas 125I-insulin release from the cells continued at 30 +/- 3% of the rate at 37 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D001011:Aorta / Q000378:metabolism; D001692:Biological Transport; D002196:Capillaries / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D007328:Insulin / Q000378:metabolism*; D007457:Iodine Radioisotopes; D007700:Kinetics; D008985:Monensin / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism*
chemical_list: D007328:Insulin; D007457:Iodine Radioisotopes; D008985:Monensin; D011972:Receptor, Insulin