Effects of arachidonic acid, PGF2 alpha, and a PGH2 analogue on airway diameters in dogs.

The effects of intravenous arachidonic acid, a prostaglandin H2 analogue [(15S)-hydroxyl-11 alpha, 9 alpha-(epoxymethano)prosta-5Z,13E-dienoic acid (PGH2-A)], and prostaglandin F2 alpha (PGF2 alpha) on lung mechanics and airway diameters were compared using tantalum bronchography in 20 paralyzed, artificially ventilated, pentobarbital-anesthetized dogs. These agents produced dose-related increases in lung resistance (RL) and decreases in dynamic compliance (Cdyn). Both RL and Cdyn changed maximally within 25 s after injection. RL, however, returned to base line within 2 min, whereas the decrease in Cdyn persisted much longer. Changes in the diameter of airways less than 2 mm produced small changes in RL and Cdyn. Larger changes in RL corresponded with changes in airways as large as 4 mm. Vagal reflexes or pulmonary edema were not important contributors to these effects. These data suggest that the changes in RL and Cdyn produced by intravascular injections of arachidonic acid, PGH2-A, and PGF2 alpha result from their direct effects on smooth muscle in airways as large as 4 mm.