Neuraminidase treatment of adrenal cells increases their response to cholera enterotoxin

Abstract

A PRIMARY action of cholera enterotoxin is to increase adenyl cyclase activity in the intestine and the elevated levels of cyclic AMP are thought to be responsible for the water loss and dehydration associated with cholera^1–4. Enterotoxin also stimulates a variety of other tissues including cultured adrenal tumour cells^5,6. In these instances the actions of the toxin are very similar to those hormones whose effects are mediated through regulation of intracellular cyclic AMP in their target tissues. A common characteristic of the hormonal responses, however, is that cyclic AMP levels are usually raised within a few seconds whereas the response to enterotoxin, in all the tissues tested, is always accompanied by a lag period of at least several minutes. We have shown previously that pretreatment of isolated rat adrenal cells with neuraminidase reduces the response to ACTH indicating that membrane sialic acid may be involved in stimulation of adenyl cyclase by this hormone^7,17 We report here that in sharp contrast to the results obtained with ACTH, the response of adrenal cells to enterotoxin is markedly enhanced by treatment with neuraminidase.