Bronchodilator activity in vivo and in vitro of four 13,14-didehydro-PGE2 analogues.

The bronchodilator activity of four analogues of PGE2: 13,14-didehydro-PGE2 (I), 20-methyl-13,14-didehydro-PGE2 (II), 16 S-methyl-13,14-didehydro-PGE2 (III) and 16 R-methyl-13,14-didehydro-PGE2 (IV) was studied in vivo and in vitro. The potency of III and IV when administered by aerosol to conscious guinea pigs was four times that of PGE2 in protecting against histamine-induced convulsion; I and II were less active. Compound III administered by aerosol to anaesthetized guinea pigs was six times more potent than PGE2 in protecting against i.v. histamine-induced increase of intractracheal pressure and the effect was longer-lasting. All the compounds caused relaxation of carbachol-induced tone in isolated guinea pig tracheal strips.