Vascular smooth muscle activity of 7-oxa-13-prostynoic acid

The effects of 7-oxa-13-prostynoic acid (7-OPA), alone and as an antagonist of PGE2 and PGF2alpha, were investigaed in isolated rabbit aortic and canine renal arterial (diameter approximentaly 0.5 mm) strips. 7-OPA caused contractions in both preparations; threshold concentrations were 3- to 10-fold higher than the PGs and maximum contraction was 50-60%. In concentrations of 10(-5) M, 7-OPA inhibited contractions by PGF2alpha and PGE2. The same concentration of 7-OPA did not inhibit norepinephrine-induced contractions. These data indicate that 7-OPA is a partial agonist of PG receptors and produces its antagonism of PGE2 and PGF2alpha by that mechanism.