Effects of cholera enterotoxin on adenosine 3',5'-monophosphate and neutrophil function. Comparison with other compounds which stimulate leukocyte adenyl cyclase

Abstract

Cholera enterotoxin caused a delayed accumulation of adenosine 3',5'-monophosphate (cyclic AMP) in human leukocytes, associated with an increase in leukocyte adenyl cyclase activity. The action of cholera enterotoxin contrasted with that of other agents which stimulate adenyl cyclase: (a) the effects of the toxin were delayed in onset, while prostaglandin-E(1) (PGE(1)) and isoproterenol acted rapidly; (b) removal of the soluble toxin from the extracellular medium did not abolish its effects on cyclic AMP and inhibition of antigenic histamine release, while removal of PGE(1) did prevent its effects; (c) PGE(1), but not cholera enterotoxin, stimulated adenyl cyclase activity when added directly to broken cell preparations. Binding of the toxin to leukocytes was rapid and irreversible, and was followed by a gradual increase in cyclic AMP which was not prevented by cycloheximide. Cholera enterotoxin caused accumulation of cyclic AMP in purified human neutrophils as well as mono-nuclear cells, but did not prevent the extrusion of lysosomal hydrolases from phagocytic cells. The toxin only slightly inhibited the ability of human neutrophils to kill Candida albicans. Thus these results with the toxin cast doubt on previous proposals that cyclic AMP regulates these two functions of neutrophils. The unique action of cholera enterotoxin on cyclic AMP production provides a potentially useful pharmacologic tool, in addition to methylxanthines and dibutyryl cyclic AMP, for testing hypotheses relating cyclic AMP to altered function of leukocytes and, perhaps, of other mammalian cells.