ALANINE UPTAKE BY THE ENDOTHELIUM OF CANINE BLOOD-VESSELS AND BY THE VESSELS OF HUMAN UMBILICAL-CORD

In order to determine whether the endothelium of vascular wall fragments possesses an active uptake mechanism for alanine identical to the one present in endothelial cells in tissue culture samples of canine aorta, carotid artery and vena cava, human umbilical cord vessels, were incubated in vitro in the presence of labelled alanine. In a series of experiments, it was observed that all the tissues investigated accumulated a significant amount of this substrate against a concentration gradient, and that the accumulation was saturable in the presence of sodium. This uptake was sodium-dependent, was significantly inhibited by ouabain and was greatly reduced under anoxic conditions. Finally, the uptake was completely abolished by prior mechanical or osmotic destruction of the intima. In conclusion, the very reproducible measurement of active alanine uptake in fragments of blood vessels may be a valuable method of evaluating the integrity of the endothelium.