Nonlinear resistances in hepatic microcirculation

The American Journal of Physiology
R Maass-Moreno, C F Rothe

Abstract

The liver provides a reservoir available for mobilizing large amounts of blood, but if a change in downstream (outflow) pressure below a certain magnitude (break pressure) does not change upstream pressures, blood volume redistribution may be limited. For downstream pressures larger than the break pressure, the upstream pressures change proportionately. We tested the hypothesis that this nonlinear mode of pressure transmission could be found from the abdominal vena cava to the hepatic microcirculation and from the hepatic microcirculation to the portal vein. Using a servo-null micropipette technique, we measured microvascular pressures at the liver surface of rabbits. In 16 of 30 measurements, increasing the pressure at the liver outflow, by partially occluding the caudal thoracic vena cava, caused an increase in hepatic venular pressure only after the abdominal vena caval pressure exceeded a break pressure of 2.85 +/- 0.92 mmHg. In 13 of 31 measurements, portal venous pressure was not changed until the hepatic venular pressure exceeded a break pressure of 3.36 +/- 0.54 mmHg. Similar behavior and values were obtained for sinusoids and portal venules. When present, the sharp inflection in the upstream-downstream pressure plots s...Continue Reading

Citations

Oct 12, 2007·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·Toshishige ShibamotoHideaki Tsuchida

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