Endothelium‐derived relaxing factor contributes to the regulation of endothelial permeability

To determine whether endothelium‐derived relaxing factor (EDRF) contributes to the regulation of endothelial permeability, the transendothelial flux of 14 C‐su‐crose, a marker for the paracellular pathway across endothelial monolayers (Oliver, J. Cell. Physiol. 145:536–548, 1990), was examined in monolayers of bovine aortic endothelial cells grown on collagen‐coated filters. The permeability coefficient of 14 C‐sucrose was significantly decreased by 10 −3 M 8‐Bromoguanosine 3′,5′‐cyclic monophosphate or by 5 × 10 −6 M glyceryl trinitrate, an activator of soluble guanylate cyclase. Depletion of L‐arginine from endothelial monolayers increased 14 C‐sucrose permeability from 3.21 ± 0.59 to 3.88 ± 0.50 × 10 −5 cm · sec −1 (mean ± SEM; n = 6; P < 0.05). The acute administration of 5 × 10 −4 M L‐arginine to monolayers depleted of this amino acid decreased 14 C‐sucrose permeability from 2.91 ± 0.27 to 2.52 ± 0.26 × 10 −5 cm · sec −1 (n = 11; P < 0.05). 14 C‐sucrose permeability was increased by 10 −7 M bradykinin and this effect was enhanced by the presence of each one of the following compounds: 10 −5 M methylene blue, 4 × 10 −6 M oxyhemoglobin, 5 × 10 −4 M N G ‐methyl‐L‐arginine or 5 × 10 −4 M N ω ‐nitro‐L‐arginine. These results suggest that EDRF contributes to the sealing of the endothelial monolayer and that EDRF released by bradykinin acts as a feedback inhibitor attenuating the increase in endothelial permeability induced by this peptide. Because endothelial cells have the ability to contract and relax and possess guanylate cyclase responsive to nitric oxide, our results suggest that EDRF decreases 14 C‐sucrose permeability by relaxing endothelial cells, thereby narrowing the width of endothelial junctions. © 1992 Wiley‐Liss, Inc.