P(1),P(4)-Diadenosine 5'-tetraphosphate modulates l-arginine and l-citrulline uptake by bovine aortic endothelial cells

We have previously demonstrated that P(1),P(4)-diadenosine 5'-tetraphosphate (Ap(4)A) interacts with high-affinity and low-affinity binding sites on the bovine aortic endothelial cell (BAEC) surface. In this report we demonstrate that Ap(4)A interaction with the lower affinity site modulates l-arginine (l-Arg) and l-citrulline (l-Cit) uptake by BAEC. Competition uptake studies demonstrate that l-Arg and l-Cit uptake occurs through a common transporter system that is sensitive to Ap(4)A. Evidence is also presented that is consistent with Ap(4)A modulating l-Arg uptake by increasing the affinity of l-Arg for the transporter.