Effects of arachidonic acid, PGF2α), and a PGH₂ analogue on airway diameters in dogs

The effects of intravenous arachidonic acid, a prostaglandin H₂ analogue [(15S)-hydroxyl-11α,9α-(epoxymethano)prosta-5Z,13E-dienoic acid (PGE₂-A)], and prostaglandin F(2α) (PGF(2α)) 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 PGF(2α) result from their direct effects on smooth muscle in airways as large as 4 mm.