EFFECT OF CELL SHRINKAGE ON PERMEABILITY OF CULTURED BOVINE AORTIC ENDOTHELIA AND FROG MESENTERIC CAPILLARIES

1. We have tested the hypothesis that a reduction in endothelial cell volume increases microvessel permeability and that the degree of endot helial cell attachment to their basement membranes determines the magn itude of permeability changes caused by a reduction in endothelial cel l volume. 2. A decrease in endothelial cell volume was imposed on both intact microvessels and cultured endothelial monolayers by raising os molarity by 100 mosmol 1(-1). 3. We found that hypertonic solutions di d not increase the hydraulic permeability (L-p) of individually perfus ed venular microvessels in frog mesentery when the perfusate contained albumin. Hypertonic solutions did increase L-p, however, after we per fused the microvessels with the peptide Gly-Arg-Gly-Asp-Thr-Pro (GRGDT P; 0.3 mmol1(-1)), to disrupt integrin-dependent endothelial cell (EC) attachment to the extracellular matrix (ECM). 4. After albumin was re moved from the perfusate, hypertonic solutions increased L-p of microv essels and the permeability of endothelial monolayers to alpha-lactalb umin. 5. Our findings indicate that endothelial cell integrin-ECM bind ing plays a role in transducing changes in cell volume and/or shape in to changes in permeability. We hypothesize that removal of albumin fro m the vascular perfusate may compromise EC-ECM interactions via an int egrin-dependent mechanism.