Selective blockade of the vasodepressor response to prostaglandin F2α in the anaesthetized rabbit

Abstract

1 The prostaglandin-blocking activity of meclofenamic acid, N-(2,6-dichloro-m-tolyl)anthranilic acid (CI-583), was analysed in the anaesthetized rabbit. PGF_2α, PGE₁ and isoprenaline were injected before and after meclofenamic acid infusion. 2 Isoprenaline produced a fall in blood pressure, a reduction in oviduct motility and a reduction in uterine motility if the uterus showed marked spontaneous motility. PGF_2α uniformly produced a fall in blood pressure and an increase in both uterine and oviduct contractility. PGE₁ produced a fall in blood pressure, a reduction in oviduct motility and no consistent effect on uterine motility. 3 Meclofenamic acid selectively blocked the vasodepressor response to PGF_2α. The vasodepressor responses to PGE₁ and isoprenaline as well as the effects of all three agonists on uterine and oviduct contractility were not reduced by treatment with meclofenamic acid. 4 Polyphloretin phosphate (PPP) administered to two rabbits in a cumulative dose of 94 mg/kg showed no significant blocking action on the vasodepressor or uterine and oviduct contractor responses to PGE₁ or PGF_2α though this compound, like meclofenamic acid, has been reported to antagonize the actions of PGE₁ and PGF_2α on isolated smooth muscle preparations.