title: Vascular transport of insulin to rat cardiac muscle. Central role of the capillary endothelium.
abstract: Using intact, beating hearts, we have assessed the interaction of insulin with capillary endothelium and the subsequent appearance of insulin in cardiac muscle. Rat hearts were perfused with 125I-insulin (10(-10) M) alone or in combination with unlabeled insulin (10(-9)-10(-5) M). 125I grains (shown to represent greater than 90% intact insulin) over both capillary endothelium and cardiac muscle decreased in a dose-dependent manner when hearts were co-perfused with labeled insulin and increasing concentrations of unlabeled insulin. Perfusion of 125I-desoctapeptide (DOP) insulin, a low affinity insulin analogue, with unlabeled insulin (10(-9)-10(-5) M) had no effect on the appearance of 125I-DOP insulin over microvessel endothelium and muscle. When capillary receptors were first destroyed by trypsin treatment or blocked by anti-receptor antibodies, the appearance of 125I-insulin in cardiac muscle decreased proportional to the inhibition of insulin binding to the capillary receptors. We conclude that insulin binding to capillary endothelial receptors is a central step in the transport of intravascular insulin to rat cardiac muscle.
authors.affiliation: Department of Internal Medicine, Veterans Administration Medical Center, Iowa City, Iowa 52240.
authors.forename: R S
authors.initials: RS
authors.lastname: Bar
authors.forename: M
authors.initials: M
authors.lastname: Boes
authors.forename: A
authors.initials: A
authors.lastname: Sandra
mesh_terms: D000818:Animals; D001345:Autoradiography; D001692:Biological Transport; D002196:Capillaries / Q000378:metabolism; D003331:Coronary Vessels / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D007365:Intercellular Junctions / Q000502:physiology; D008297:Male; D008854:Microscopy, Electron; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*; D014357:Trypsin
chemical_list: D007328:Insulin; D011972:Receptor, Insulin; D014357:Trypsin