Specific hemodynamic effects of PGE2 and PGF1 alpha in the canine lung

The differential effects of two pulmonary vasoconstrictors, prostaglandin E2 (PGE2) and F1 alpha (PGF1 alpha) on capillary pressure and the distribution of vascular resistance were studied in isolated, blood perfused canine lung lobes. Each lobe was inflated to a constant airway pressure (3 cmH2O) and perfused in Zone III conditions at constant flow (431 +/- 36 ml/min). Pulmonary arterial and venous pressures were measured at the inflow and outflow orifices, respectively. Pulmonary capillary pressure (Pc) was determined via a double occlusion technique and pre- and postcapillary resistances calculated. PGE2 and PGF1 alpha, administered as rapid intra-arterial boluses (10-300 micrograms), increased arterial pressure in a dose-dependent fashion. However, at each dose, the increase in vascular resistance was more pronounced in postcapillary segments. The increase in postcapillary resistance was 5 and 3.5 times greater than the increase in precapillary resistance at the highest dose of PGE2 and PGF1 alpha used in this study, respectively (300 micrograms). As a result, Pc measured at the peak of the vascular response increased by 2 to 19 cmH2O over control values with PGE2 and by 5 to 13 cmH2O over control values with PGF1 alpha as the prostaglandin dose was varied from 10 to 300 micrograms. We conclude that the predominant effect of these prostanoids is to increase postcapillary resistance and pulmonary capillary pressure.