EFFECTS OF ANAPHYLAXIS MEDIATORS ON PARTITIONED PULMONARY VASCULAR-RESISTANCE DURING RAGWEED SHOCK IN DOGS

We examined the effect of anaphylactic shock on the longitudinal distr ibution of pulmonary vascular resistance (PVR) in ragweed-sensitized d ogs in which PVR was partitioned into an upstream arterial component ( Rus) and a downstream venous and capillary component (Rds). We also as sessed whether Rus and Rds would be reduced by pretreatment with hista mine H-1- and H-2-receptor blocking agents and with cyclooxygenase and lipoxygenase pathway inhibitors. Anesthetized animals were examined o n separate occasions 3 wk apart in which one of the treatments was ran domly given. The pulmonary arterial occlusion technique was used to de termine segmental pressure drops. During ragweed challenge, PVR increa sed approximate to 4 times compared with the preshock value (3.04 vs. 12.07 mmHg.l(-1).min: P < 0.05). Although both Rus and Rds increased p ostshock, the greatest relative increase occurred in Rds. None of the treatments reduced partitioned resistances compared with no treatment. Our results show that, under conditions of anaphylactic shock, increa ses in Rus and Rds could not be ascribed to release of histamine or pr oducts of the cyclooxygenase and lipoxygenase pathways.