The effect of cAMP on ion transport in Fallopian tube epithelial cells in vitro

The coupled movement of ions and water across epithelia determines the comp osition and volume of fluid present in the lumen of organs. The second mess enger cAMP is important in effecting electrolyte and water transport in man y transporting epithelia; however, its role in Fallopian tube transport is uncertain. We have conducted electrophysiological studies on Fallopian tube epithelial cell monolayers in Ussing chambers and have demonstrated that e xogenously added cAMP and agents that generate its intracellular production results in an increase in short-circuit current consistent with the transp ort of net electrical charge from a basal to mucosal direction. In contrast to the known effects of ATP in this tissue, the increase in short-circuit current was not explicable in terms of electrogenic chloride secretion as i t was not affected by the chloride channel inhibitors, 4-acetamido-4'-isoth iocyanostilbene-2,2-disulphonic acid 1 mmol/l (SITS) and frusemide. Instead the current was reduced by the sodium channel inhibitor, amiloride, and wa s therefore, in part, explicable in terms of electrogenic Na+ absorption. T hese findings will enhance our understanding of the physiological mechanism s responsible for human Fallopian tubal fluid formation and composition.