Characterization of Murine Vasopressor and Vasodepressor Prostaglandin E 2 Receptors

Four E-prostanoid (EP) receptors, designated EP(1), EP(2), EP(3), and EP(4), mediate the cellular effects of prostaglandin E(2) (PGE(2)). The present studies pharmacologically characterize the vasopressor and vasodepressor EP receptors in wild-type mice (EP(2)(+/+) mice) and mice with targeted disruption of the EP(2) receptor (EP(2)(-/-) mice). Mean arterial pressure (MAP) was measured via a carotid artery catheter in anesthetized male mice. Intravenous infusion of PGE(2) decreased MAP in EP(2)(+/+) mice but increased MAP in EP(2)(-/-) mice. Infusion of EP(3)-selective agonists, including MB28767, SC46275, and sulprostone, increased MAP in both EP(2)(+/+) and EP(2)(-/-) mice. Pretreatment with SC46275 desensitized mice to the subsequent pressor effect of sulprostone, but the vasodepressor effect of PGE(2) in EP(2)(+/+) mice remained intact. Although PGE(2) alone increased MAP in EP(2)(-/-) mice, prior desensitization of the pressor effect with SC46275 allowed a residual vasodepressor effect of PGE(2) to be seen in the EP(2)(-/-) mice. An EP(4)-selective agonist (prostaglandin E(1)-OH) functioned also as a vasodepressor in both EP(2)(-/-) and EP(2)(+/+) mice. High levels of EP(3) receptor mRNA were detected in mouse aortas and rabbit preglomerular arterioles by nuclease protection, with lower expressions of EP(1), EP(2), and EP(4) mRNA. The findings suggest that combined vasodepressor effects of EP(2) and EP(4) receptors normally dominate, accounting for the depressor effects of PGE(2). In contrast, in EP(2)(-/-) mice, EP(4) receptor activity alone is insufficient to overcome the EP(3) vasopressor effect. These findings suggest that a balance between pressor and depressor PGE(2) receptors determines its net effect on arterial pressure and that these receptors may be important therapeutic targets.