Microvascular pressures and filtration coefficients in the cat mesentery.

Abstract

Filtration coefficient and hydrostatic pressure were measured in single capillaries and venules in the cat mesentery using a modification of the Landis single vessel occlusion technique. Venules were filtering fluid, not absorbing it as often supposed. The mean filtation coefficient in capillaries was 0.018 .mu.m/s .cntdot. mmHg-1 (1.35 .times. 10-10 m/s .cntdot. Pa-1 [arterial pressure]) while that in venules was 0.027 .mu.m/s .cntdot. mmHg-1 (2.02 .times. 10-10 m/s .cntdot. Pa-1). In both capillaries and venules, filtration coefficient increased with decreasing pressure. The difference between directly measured venular pressure and that calculated from the occlusion data was used to determine the contribution of the interstitium to fluid exchange. In the mesentery superfused with Krebs solution the tissue pressure so determined was zero or subatmospheric initially but became increasingly positive with lengthening exposure of the mesentery.