Capillary filtration coefficient, vascular resistance, and compliance in isolated mouse lungs

Although many recently produced transgenic mice possess gene alterations af fecting pulmonary vascular function, there are few baseline measurements of vascular resistance and permeability. Therefore, we excised the lungs of C 57/BL6 mice and perfused them with 5% bovine serum albumin in RPMI-1640 cul ture medium at a nominal flow of 0.5 ml/min and ventilated them with 20% O- 2-5% CO2-75% N-2. The capillary filtration coefficient, a sensitive measure ment of hydraulic conductivity, was unchanged over 2 h (0.33 +/- 0.03 ml . min(-1) . cmH(2)O(-1) . 100 g(-1)) in a control group ventilated with low p eak inflation pressures (PIP) but increased 4.3-fold after high PIP injury. Baseline pulmonary vascular resistance was 6.1 +/- 0.4 cmH(2)O . ml(-1) . min . 100 g(-1) and was distributed 34% in large arteries, 18% in small art eries, 14% in small veins, and 34% in large veins on the basis of vascular occlusion pressures. Baseline vascular compliance was 5.4 +/- 0.3 ml . cmH( 2)O(-1) . 100 g(-1) and decreased significantly with increased vascular pre ssures. Baseline pulmonary vascular resistance was inversely related to bot h perfusate flow and microvascular pressure and increased to 202% of baseli ne after infusion of 10(-4) M phenylephrine due to constriction of large ar terial and venous segments. Thus isolated mouse lung vascular permeability, vascular resistance, and the longitudinal distribution of vascular resista nce are similar to those in other species and respond in a predictable mann er to microvascular injury and a vasoconstrictor agent.