INHIBITION OF PROSTAGLANDIN SYNTHESIZING ENZYMES BY HAPTOGLOBIN AND PLASMA OF RATS WITH INFLAMMATION

Abstract

Administration of carrageenin or adjuvant to rats to induce inflammation produced increases in the plasma haptoglobin level. Simultaneously, there was an increase in the activity of the plasma inhibitor of prostaglandin E₂ synthesis. Partially purified haptoglobin inhibited the microsomal over-all conversion of arachidonic acid to prostaglandin E₂. The addition of the haptoglobin inhibited two heme-dependent reactions catalyzed by a purified enzyme of seminal vesicle microsome, i.e., the prostaglandin G₂ synthesis from arachidonic acid and the conversion of prostaglandin G₂ to H₂. However, the plasma inhibitory activity was accounted for only partially by the haptoglobin contained in the plasma from treated rats.