Characteristics of prostaglandin E 1 potentiation of inflammatory activity of some agents

Abstract

In rats pretreated with indomethacin, injection of PGE 1 (prostaglandin E 1) with carrageenan potentiated the carrageenan paw oedema. This effect of PGE 1, was maximal when it was injected together with carrageenan, there being a reduction in the action of PGE 1 if carrageenan injection was delayed after PGE 1 injection. PGE 1 induced potentiation of increase in plasma protein leakage induced by intradermal injections of bradykinin and histamine also depended on the injection of PGE 1 along with these agents. Thus oedema enhancement by PGE 1 differs from its action in pain, where PGs cause a long lasting sensitization of the injected area for the actions of other algesics. Since vasodilation may be a mechanism of oedema enhancement by PGs, the ability of adenosine and papaverine to mimic PGE 1 in paws and skins of rats were examined. Adenosine was active whereas papaverine was inactive in this respect. To clarify this difference, the vasodilatory properties of PGE 1, adenosine and papaverine were assessed by their ability to antagonize NA response in perfused rat mesenteric blood vessels. Only papaverine was effective in antagonising the NA response. Thus, PGE 1 and adenosine which potentiated the oedema inducing actions of other agents showed no vasodilatory properties and papaverine, a vasodilator, had no oedema potentiating actions.