ARG-GLY-ASP PEPTIDE INCREASES ENDOTHELIAL HYDRAULIC CONDUCTIVITY - COMPARISON WITH THROMBIN RESPONSE

The contribution of integrin receptors to the regulation of endothelia l permeability was studied using cultured bovine pulmonary microvascul ar endothelial cell (BPMVEC) monolayers by the measurement of hydrauli c conductivity (L(p)). Treatment of monolayers with a peptide containi ng the sequence Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) (0.85 mM) to compete for the RGD sequence of extracellular matrix (ECM) proteins increased endothelial L(p) threefold, whereas the control peptide Gly-Arg-Gly-Gl u-Ser-Pro had no effect on L(p). This action of GRGDSP on L(p) was not significantly altered by dibutyryl adenosine 3',5'-cyclic monophospha te (DBcAMP; 0.5 mM). Endothelial L(p) increased twofold when the monol ayers were challenged with a-thrombin (5 x 10(-8) M for 10 min), and t his response was completely reversed by DBcAMP. The strength of adhesi on of endothelial cells was estimated by evaluating the ability of end othelial cells to remain attached to ECM after treating the monolayers with 0.05% trypsin plus 0.5 mM EDTA. Exposure of the monolayers to ei ther GRGDSP or alpha-thrombin significantly reduced the strength of ad hesion to the ECM. DBcAMP prevented the antiadhesive effect of alpha-t hrombin but not that of GRGDSP. Treatment of the monolayers with eithe r alpha-thrombin or GRGDSP caused formation of intercellular gaps, but only the thrombin-induced intercellular gaps were accompanied by reor ganization of actin filaments. These results indicate that integrin bi nding to ECM proteins regulates an important determinant of endothelia l permeability and that alpha-thrombin and GRGDSP increase endothelial cell monolayer permeability by different mechanisms.