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 demonstra te that Ap(4)A interaction with the lower affinity site modulates L-arginin e (L-Arg) and L-citrulline (L-Cit) uptake by BAEC. Competition uptake studi es demonstrate that L-Arg and L-Cit uptake occurs through a common transpor ter 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 o f L-Arg for the transporter. (C) 2000 Academic Press.