Effects of prostaglandin endoperoxide analogs on contractile elements in lung and gastrointestinal tract

Prostaglandin endoperoxides are formed in the lung as intermediate compounds in the biosynthesis of prostaglandins and thromboxanes. The effects of different doses of two analogs of prostaglandin endoperoxide PGH2 were compared with those of PGF2alpha and PGE2 on superfused preparations of isolated trachea, bronchiole, peripheral lung, pulmonary artery and gastrointestinal smooth-muscle tissues. Endoperoxide analogs induced contraction of all smooth-muscle structures in the lung and airway. Compared to PGF2alpha, analog I was approximately 71 times as potent on guinea-pig trachea, 214 times as potent on guinea-pig lung, and 57 times as potent on guinea-pig pulmonary artery. Analog II was moderately less potent on all tissues than analog I. On gastrointestinal smooth-muscle organs, the PGH2 analogs were generally closer in activity to PGF2alpha and PGE2, or even weaker. The findings show that PG endoperoxide analogs are potent constrictors of airways, lung and pulmonary vessels, and suggest that the naturally occurring compounds may participate in the mediation of bronchoconstriction and pulmonary vasoconstriction in disease states.