5-trans U-46619 is a minor impurity (2-5%) which variably exists in most commercial preparations of U-46619 [1]. U-46619 is a selective thromboxane A2 agonist involved in inducing platelet aggregation and vascular smooth muscle contraction [2].
The biological activity of 5-trans U-46619 has been rarely tested separately from U-46619 itself. In the only case published to date, 5-trans U-46619 was found to be a about half as potent an inhibitor of Prostaglandin E synthase as the 5-cis version of U-46619 [1]. Thromboxane A2 (TxA2) has been involved in the pathogenesis of airway hyperresponsiveness. TXA2 is a type of thromboxane produced by activated platelets and shows prothrombotic properties. Thromboxane A2 has also been known as a vasoconstrictor and is especially important during tissue injury and inflammation [3].
References:
[1] Quraishi O, Mancini J A, Riendeau D. Inhibition of inducible prostaglandin E 2 synthase by 15-deoxy-Δ 12, 14-prostaglandin J 2 and polyunsaturated fatty acids[J]. Biochemical pharmacology, 2002, 63(6): 1183-1189.
[2] Coleman, R. A.,Humphrey, P.P.A.,Kennedy, I., et al. Comparison of the actions of U-46619, a prostaglandin H2-analogue, with those of prostaglandin H2 and thromboxane A2 on some isolated smooth muscle preparations. British Journal of Pharmacology 73, 773-778 (1981).
[3] Svensson J, Strandberg K, Tuvemo T, et al. Thromboxane A2: Effects of airway and vascular smooth muscle[J]. Prostaglandins, 1977, 14(3): 425-436.