Control of the arteriolar myogenic response by transmural fluid filtration

Mechanisms of the myogenic response have not been completely established. We hypothesize that transmural fluid filtration from plasma across smooth muscle cells and into the surrounding interstitium helps regulate arteriolar myogenic tone. Arteriolar diameters in the rat mesentery were monitored prior to and following vascular occlusion with a glass micropipette. Arteriolar occlusion not only gave an increase in hydrostatic pressure that initiated a myogenic response upstream of the pipette, but also allowed measurement of fluid filtration rate by monitoring the movement of vascular red blood cells. A statistically significant correlation existed between basal myogenic tone and fluid filtration. Additionally, the myogenic response was attenuated when an osmotic solution of albumin and ficoll was infused into the bloodstream to decrease fluid filtration. These results are consistent with the hypothesis that shear stress on arteriolar smooth muscle, induced by transmural fluid filtration, is a contributing factor that helps control myogenic tone.