The effect of adenosine triphosphate on the transmural potential in rat small intestine.

1. ATP either in the mucosal or serosal fluid caused a transient increase in the potential difference and short-circuit current across the wall of rat jejunum in vitro, the serosal solution becoming more positive.2. Similar responses were observed in the ileum and colon, and in in vivo preparations of small intestine.3. The response is relatively specific for ATP.4. The transient nature of the response is not due to rapid hydrolysis of extracellular ATP.5. High concentrations of K(+) in the mucosal medium, serosal ouabain or mucosal 2,4-dinitrophenol all inhibit the response without altering the time course.6. Significant inhibition was not observed in the presence of ADP or in Mg(2+)-free salines.7. The results are consistent with an intracellular action of ATP in the epithelium to stimulate net ion transport. The results do not demonstrate whether or not extracellular ATP can act as an energy donor for an electrogenic ion pump.8. Theophylline prolongs the time course of the response, and the involvement of the adenyl cyclase system cannot be excluded as an explanation for the findings.