TRANSPORT OF 2-AMINOISOBUTYRIC ACID IN CULTURED ENDOTHELIAL-CELLS

Conflicting reports exist concerning the presence of a Na+-coupled ami no acid transport system in cultured endothelial cells. We have employ ed a non-metabolizable analog, 2-aminoisobutyric acid (AIB), to invest igate the activity of Na+-dependent amino acid transport in cultured h uman umbilical vein endothelial cells (HUVEC). We found a pronounced s aturable, Na+-dependent component of AIB uptake in 'fresh' (non-starve d) HUVEC. The Na+-dependent component accounted for 78% of total AIB u ptake with a high sensitivity to external Na+. The accumulation of AIB was inhibited by ouabain preincubation, consistent with the energetic s of Na+-coupled transport. Amiloride, an epithelial Na+ channel block er, also inhibited AIB transport at high concentration. The results st rongly support the presence of a Na+-coupled transport system of amino acid in HUVEC.