INTERACTION BETWEEN NITRIC-OXIDE AND PROSTAGLANDIN SYNTHESIS IN THE ACUTE-PHASE OF ALLERGIC CONJUNCTIVITIS

Both nitric oxide and prostaglandins induce vasodilatation which is an important feature of local inflammation. The purpose of the study des cribed here was to investigate a possible interaction between these tw o types of mediators in an experimental model of allergic conjunctivit is. A conjunctival allergic reaction was induced with antigen in sensi tized guinea pigs. Conjunctival vascular permeability changes were eva luated with the prophylactic use of an inhibitor of nitric oxide synth ase (L-NAME) and a cycloxygenase inhibitor (indomethacin). To study a possible interaction between nitric oxide and prostagIandin synthesis in the acute phase of allergic conjunctivitis, the levels of nitrite a nd PGE(2) were determined in lavage fluid. The prophylactic use of L-N AME on the formation of conjunctival edema in response to topical PGD( 2) administration was studied by measurement of albumin levels in lava ge fluid. Both nitric oxide and PGE(2) are synthesized in response to antigen provocation and after histamine administration. Nitric oxide a nd PGE(2) are produced simultaneously in the conjunctiva and they show ed identical synthesis profiles in response to antigen provocation. Pr etreatment with L-NAME inhibited the synthesis of PGE(2) whereas exoge nous administration of nitric oxide increased the level of PGE(2) in l avage fluid. Prophylactic treatment with L-NAME significantly inhibite d the PGD(2) induced albumin extravasation. Nitric oxide seems to play an important role in the acute phase of allergic conjunctivitis it ma y stimulate PGE(2) production and acts as a secondary mediator in PGD( 2) and histamine induced conjunctival edema.