Network assessment of capillary hydraulic conductivity after abrupt changes in fluid shear stress

Intact capillaries are composed of endothelial cells that experience continuous fluid shear stress as blood flows. Endothelial cells grown in culture demonstrate changes in barrier function in response to changes in shear stress. Therefore, it was hypothesized that intact capillaries would alter filtration in response to changes in fluid shear stress. Capillaries (n = 25) located in frog mesentery were classified according to flow direction as arteriolar, true, or venular and cannulated at 30 cm H2O to induce an abrupt change in shear stress. Frog and human red blood cells acted as velocity markers before and after cannulation, respectively, for calculating fluid shear stress. Hydraulic conductivity (Lp) was measured at 30 cm H2O following a change in shear stress and ranged from 0.7 to 96. 8 x 10(-7) cm s-1 cm H2O-1. For true and venular capillaries, Lp was related to the magnitude of the shear stress stimulus and accounted for the wide range in absolute values of Lp. Arteriolar capillaries did not respond to the mechanical stimulus. These data indicate that blood flow may modulate filtration in homogeneous subpopulations of capillaries in the capillary bed.