STUDIES ON THE RELATIVE EFFECTS OF PROSTAGLANDINS, BRADYKININ, 5‐HYDROXYTRYPTAMINE AND HISTAMINE ON THE SYNOVIAL MICROCIRCULATION IN DOGS

Abstract

1 The relative effects of prostaglandins E₁, E₂, F_1α, F_2α, bradykinin, histamine and 5-hydroxytryptamine (5-HT) on the canine synovial microcirculation were investigated using the rate of clearance of radioactive xenon (¹³³Xe) as an index of synovial perfusion. 2 All the compounds tested, except prostaglandin F_1α, produced a vasodilator effect. The descending order of potency of the active compounds was (i) prostaglandin E₁, (ii) prostaglandin E₂ and bradykinin, (iii) histamine and 5-HT, (iv) prostaglandin F_2α. The most potent compound tested, prostaglandin E₁ produced an effect in nanogram amounts in each joint. 3 Prostaglandin F_2α has been reported to have an anti-inflammatory action; however no evidence was found of antagonism of prostaglandin E₁ by two dose levels of prostaglandin F_2α. 4 Preliminary studies showed that threshold doses of prostaglandin E₁ did not potentiate the vasodilator action of threshold or sub-threshold doses of bradykinin in the dog synovium.