Biological activities of prostaglandin H1 analogs

The influences of epoxymethano and epoxycarbonyl analogs of PGH₁ on washed rabbit platelets, isolated smooth muscles and perfused heart preparations were investigated. On washed rabbit platelets, 11,9-epoxy-methano and 11,9-epoxycarbonyl PGH₁ produced a platelet aggregation whereas 9,11-epoxymethano and 9,11-epoxy-carbonyl PGH₁ produced an inhibition of arachidonic acid-induced platelet aggregation. On isolated rabbit thoracic aorta strips, 9,11-epoxycarbonyl PGH₁ showed strong contracting activity (5 times as active as 11,9-epoxy-methano PGH₂ and 31 times as active as PGH₂). All the analogs of PGH₁ caused contraction of guinea pig tracheal muscle and caused an increase of perfusion pressure in guinea pig heart, though 11,9-epoxymethano and epoxy-carbonyl PGH₁ were far more active than 9,11-epoxymethano and epoxycarbonyl PGH₁. Differences in biological activities between 11,9-epoxymethano and epoxycarbonyl PGH₁, and 9,11-epoxymethano and epoxycarbonyl PGH₁ indicate that the orientation of functional groups at C₉ and C₁₁ influences biological activities.