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A Shear Stress Component to the Modulation of Capillary Hydraulic Conductivity (L p )
Author(s) -
Williams Donna A.
Publication year - 1996
Publication title -
microcirculation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.793
H-Index - 83
eISSN - 1549-8719
pISSN - 1073-9688
DOI - 10.3109/10739689609148293
Subject(s) - capillary action , shear stress , chemistry , pipette , starling , shear (geology) , shear rate , materials science , anatomy , composite material , medicine , rheology
Objective : Two major factors that determine transcapillary exchange are Starling forces and hydraulic conductivity (L p ) of capillary walls. Although chemical stimuli alter L p , the influence of mechanical stimuli has been neglected. Therefore, we tested the hypothesis that the L p of intact capillaries would increase with the magnitude of changes in shear stress presented to each capillary. Methods : Capillaries ( n = 26) in the mesentery of pithed frogs ( n = 23) were cannulated at 30 cm H 2 O (average in situ pressure = 9.2) to alter shear stress. For the calculation of shear stress, velocities of both frog red blood cells (RBC) and human RBC in the pipette solution were measured in each capillary before and after cannulation, respectively. L p was assessed 2 min after cannulation. Results : Venular capillaries only responded to the changes in shear stress. The magnitude of the changes in shear stress correlated positively with the values for capillary L p (Kendall's tau = 0.56; p = 0.02). Conclusions : While Starling forces influence the movement of fluid by acting perpendicular to the long axis of capillaries, shear stress acts in a plane tangential to the capillary walls and appears to alter capillary L p . In addition to chemical stimuli, the mechanical stimulation of capillaries can alter the barrier itself and consequently alter filtration rate.