Endothelial cells actively concentrate insulin during its transendothelial transport.
OBJECTIVE
We examined insulins uptake and transendothelial transport by endothelial cells in order to: (i) ascertain whether insulin accumulates within the cells to concentrations greater than in the media; (ii) compare trans endothelial insulin transport to that of inulin (using the latter as a tracer for passive transport or leaked); and; (iii) determine whether insulins transported depended on insulin action.


METHODS
Using 125I-insulin at physiologic concentrations we measured both the uptake and trans endothelial transport of insulin by bovine aortic endothelial cells and measured cell volume using tritiated 3-O-methylglucose.


RESULTS
Bovine aortic endothelial cells accumulate insulin to > five-fold above the media concentrations and the trans endothelial transport of insulin, but not inulin, is saturable and requires intact PI-3-kinase and MEK signaling.


CONCLUSIONS
The insulin receptor and downstream signaling from the receptor regulates endothelial insulin transport. Insulin is accumulated against a concentration gradient by the endothelial cell. We suggest that insulin uptake is rate limiting for insulin trans endothelial transport.
Division of Endocrinology, Department of Medicine, University of Virginia, School of Medicine, Charlottesville, VA 22908, USA.
Amanda J
AJ
Genders
Vera
V
Frison
Sarah R
SR
Abramson
Eugene J
EJ
Barrett
D000818:Animals; D002417:Cattle; D048429:Cell Size; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology
D007328:Insulin; D019869:Phosphatidylinositol 3-Kinases; D020929:Mitogen-Activated Protein Kinase Kinases
endothelium; insulin receptor; insulin transport