Influence of pH on capillary filtration coefficient of rat mesenteries perfused with solutions containing albumin.

A preparation of rat mesentery was vascularly isolated from the intestine and perfused with a physiological salt solution containing either Ficoll 70 or bovine serum albumin, to act as colloidal agents. The capillary filtration coefficient (Kf; units, ml. min-1 100 g-1 mmHg-1) was measured by following the weight change after graded increases in venous pressure. At pH values greater than 7.05, Kf, during perfusion with 3 and 4% bovine serum albumin solutions, was 0.219 +/- 0.023 (mean +/- S.E. of mean), ninety-eight observations in thirteen experiments, which was significantly less than the value of 0.507 +/- 0.038 which was obtained during perfusion with albumin solutions at pH less than 7.05, seventy-six observations in eleven experiments, (P less than 0.05). The value of Kf obtained during perfusion with 4% Ficoll solutions was 0.267 +/- 0.018, 119 observations in sixteen experiments, and remained uninfluenced by pH over the same range that had been used with the albumin solutions; however, perfusion of the tissues with Ficoll solutions at pH greater than 7.05, after perfusion with albumin solution pH less than 7.05, did cause the Ficoll-derived value of Kf to rise to 0.502 +/- 0.055, seventy-two observations in eleven experiments. It was concluded that the changes in Kf were not due to pH alone, but were mediated by albumin at acidic pH.