COMPARISON OF OZONE-INDUCED EFFECTS ON LUNG-MECHANICS AND HEMODYNAMICS IN THE RABBIT

The effects of rabbit exposure to ozone (O-3) (0.4 ppm for 4 h) on pul monary mechanical properties and hemodynamics have been investigated o n the isolated perfused lung model. Tracheal pressure, airflow, and ti dal volume were measured in order to calculate lung resistance (R-1) a nd dynamic compliance (Cdyn). Using the arterial/venous/double occlusi on method, the total pressure gradient (Delta Pt) was partitioned into four components (arterial, pre-, postcapillary and venous). Dose-resp onse curves to acetylcholine (ACh), substance P (SP), and histamine we re constructed in lungs isolated from rabbits immediately or 48 h afte r air or O-3 exposure. O-3 induced a significant increase in the basel ine value of Delta Pt, more markedly 48 h after the exposure. Immediat ely after the exposure, O-3 partly inhibited the ACh-, SP-, and histam ine-induced decreases in Cdyn and increases in R-L. This inhibitory ef fect was still in part present 48 h after O-3 treatment. In the groups studied immediately after exposure, O-3 did not significantly modify the ACh-, SP-, and histamine-induced vasoconstriction. Forty-eight hou rs after exposure, O-3 induced a contractile response to ACh and SP in the arterial segment but decreased the response to histamine. We conc lude that O-3 can induce direct vascular constriction. Directly, but a lso 48 h after exposure, O-3 can inhibit the ACh-, SP-, and histamine- induced changes in lung mechanical properties. Ozone can also induce s ome changes in the intensity and in the location of the vascular respo nses to ACh, SP, and histamine. (C) 1998 Academic Press.