Pressure, serotonin, and histamine effects on lung multiple-indicator curves in sheep

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Abstract
Increases in transvascular exchange in the lung may be important in disease processes which lead to pulmonary edema. Two methods were used to measure vascular permeability in the intact lung: the multiple-indicator dilution technique and the timed collection and protein analysis of pulmonary lymph. Indicator-dilution experiments were conducted in awake, instrumented sheep. The effects of increased capillary pressure, histamine infusion and serotonin infusion on capillary permeability were measured. The mean control value of permeability surface area product (PS) for [14C]urea measured with multiple-indicator curves was 10.2 .+-. 0.6 SE ml/s in 56 experiments. Obstruction of the mitral valve leading to increased capillary pressures had no significant effect on PS. Serotonin caused a slight increase in PS. The infusion of histamine increased PS for [14C]urea to 18.1 .+-. 1.5 SE ml/s. These values were compared to previously published permeabilities calculated for the transport of endogenous protein fractions from the plasma to the lymph in similar preparations. Histamine-caused permeability changes in the lung are measurable by multiple-indicator methods. PS values identified by multiple-indicator techniques are consistent with permeability values inferred from lymph observations. This PS sensitivity is not limited to a single model for the interpretation of PS but is exhibited by several different methods for PS calculation.