Antagonistic action of AA-2414 on thromboxane A2/prostaglandin endoperoxide receptor in platelets and blood vessels.

AA-2414, (+/-)-7-(3,5,6-trimethyl-1,4-benzoquinon-2-yl)-7-phenylheptanoi c acid, inhibited the aggregation of guinea pig platelets induced by a prostaglandin endoperoxide (PGH2) analogue, U-44069 and the specific binding of another analogue, [3H]U-46619 to washed guinea pig platelets with IC50 values of 3.1 x 10(-7) and 8.2 x 10(-9) M, respectively. AA-2414 competitively inhibited the contraction of rabbit aorta and pig coronary arteries induced by U-44069 with pA2 values of 8.3 and 9.0, respectively. AA-2414 also inhibited the contraction of rabbit aorta induced by PGF2 alpha (pA2: 7.8) and the contraction of pig coronary arteries induced by PGF2 alpha, PGD2 and 9 alpha,11 beta-PGF2 with pA2 values of 7.8, 8.6 and 7.8, respectively. But, AA-2414 had no effect on the antiaggregatory effect of PGD2 on the aggregation of guinea pig platelets. In experiments with guinea pigs ex vivo, AA-2414 (0.1-1 mg/kg, p.o.) dose-dependently inhibited the platelet aggregation induced by U-44069; the inhibition at a dose of 1 mg/kg was 100% at 1 hr and was 89% even at 24 hr after the administration. The thromboxane (TX) A2/PGH2 receptor antagonistic action of AA-2414 was stereospecific. These results show that AA-2414 is a potent, orally active and long acting TXA2/PGH2 receptor antagonist. In addition, AA-2414 has PGF2 alpha, PGD2 and 9 alpha,11 beta-PGF2 antagonistic effects.