Abstract
Previous investigations from other laboratories have indicated that arachidonic acid stimulates a rapid, dose-dependent release of hormones such as hPL and LH. To investigate the involvement of arachidonic acid in catecholamine secretion, the effect of p-bromophenacyl bromide, a phospholipase A2 inhibitor, on acetylcholine-stimulated catecholamine secretion was studied in perif used pig adrenal medulla. Such effect was blocked by pretreatment of the tissue with the phospholipase A2 inhibitor, although arachidonic acid itself caused catecholamine release from the perifused pig adrenal medulla. Exogenous arachidonic acid also induced a release of catecholamine from adrenal medullary cells in culture. Pretreatment of perifused adrenal medulla with nordihydroguaiaretic acid, a lipoxygenase inhibitor, also inhibited the increase of catecholamine output induced by acetylcholine. These results suggest that a certain arachidonic acid metabolite evokes the catecholamine release.
