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 pulmonary mechanical properties and hemodynamics have been investigated on the isolated perfused lung model. Tracheal pressure, airflow, and tidal volume were measured in order to calculate lung resistance (R(1)) and dynamic compliance (Cdyn). Using the arterial/venous/double occlusion method, the total pressure gradient (Delta Pt) was partitioned into four components (arterial, pre-, postcapillary and venous). Dose-response curves to acetylcholine (ACh), substance P (SP), and histamine were constructed in lungs isolated from rabbits immediately or 48 h after air or O(3) exposure. O(3) induced a significant increase in the baseline value of Delta Pt, more markedly 48 h after the exposure. Immediately after the exposure, O(3) partly inhibited the ACh-, SP-, and histamine-induced decreases in Cdyn and increases in R(L). This inhibitory effect 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 hours after exposure, O(3) induced a contractile response to ACh and SP in the arterial segment but decreased the response to histamine. We conclude that O(3) can induce direct vascular constriction. Directly, but also 48 h after exposure, O(3) can inhibit the ACh-, SP-, and histamine-induced changes in lung mechanical properties. Ozone can also induce some changes in the intensity and in the location of the vascular responses to ACh, SP, and histamine. (C) 1998 Academic Press.