Effects of arachidonate on permeability and resistance distribution in canine lungs

In this study, 14 canine lung lobes were isolated and perfused with autologous blood at constant pressure (CP) or constant flow (CF). Pulmonary capillary pressure (Pc) was measured via venous occlusion or simultaneous arterial and venous occlusions. Arterial and venous pressures and blood flow were measured concurrently so that total pulmonary vascular resistance (RT) as well as pre- (Ra) and post- (Rv) capillary resistances could be calculated. In both CP and CF perfused lobes, 5-min arachidonic acid (AA) infusions (0.085 +/- 0.005 to 2.80 +/- 0.16 mg X min-1 X 100 g lung-1) increased RT, Rv, and Pc (P less than 0.05 at the highest dose), while Ra was not significantly altered and Ra/Rv fell (P less than 0.05 at the highest AA dose). In five CP-perfused lobes, the effect of AA infusion on the pulmonary capillary filtration coefficient (Kf,C) was also determined. Neither low-dose AA (0.167 +/- 0.033 mg X min-1 X 100 g-1) nor high-dose AA (1.35 +/- 0.39 mg X min-1 X 100 g-1) altered Kf,C from control values (0.19 +/- 0.02 ml X min-1 X cmH2O-1 X 100 g-1). The hemodynamic response to AA was attenuated by prior administration of indomethacin (n = 2). We conclude that AA infusion in blood-perfused canine lung lobes increased RT and Pc by increasing Rv and that microvascular permeability is unaltered by AA infusion.