Diarrheagenic effect of volume expansion: intestinal fluid secretion without mucosal adenyl cyclase stimulation.

Rapid intravenous saline infusion causes secretion of isotonic fluid by the canine duodenum. The duodenal fluid secretion is not accompanied either by increased adenyl cyclase activity in the mucosal epithelial cells or by widening of the "tight junctions" between epithelial cells. These data clearly indicate that the diarrheagenic effect of volume expansion is not mediated by the adenyl cyclase system. Furthermore, these data provide support for the concept that, when increased mucosal adenyl cyclase activity is associated with gut fluid secretion, the adenyl cyclase stimulation is a primary event, and is not secondary to the transmucosal isotonic fluid movement.