ROLE OF ARACHIDONIC-ACID METABOLITES IN THE ACTION OF A BETA-ADRENERGIC AGONIST ON HUMAN MONOCYTE PHAGOCYTOSIS

The mechanisms by which beta adrenergic stimulation regulates phagocyt osis of Candida albicans by human peripheral monocytes (HPM) are chara cterized. Isoproterenol (ISO) inhibits phagocytosis in a concentration -dependent manner. This effect was blunted by propranolol, inhibitors of phospholipase A(2) (PLA(2)), cyclooxygenase and verapamil, pointing to a participation of arachidonic acid (AA) metabolites and calcium i n the phenomenon. Prostaglandin E-2 (PGE(2)) and dibutyryl cyclic AMP (db-cAMP) also exerted the same inhibitory effect on phagocytosis. ISO interacts with beta adrenergic receptors of HPM increasing PGE(2) and cAMP. We conclude that the mechanisms by which beta adrenergic stimul ation regulates phagocytosis of Candida albicans by HPM appear to be s econdary to beta adrenoceptor-mediated hydrolysis of AA accompanied by an increase in PGE(2) generation and cAMP production. Both PGE(2) and cAMP could act as mediators of the inhibitory action of beta agonists on the HPM-phagocytosis process.