Effects of cholera toxin on villous tissue osmolality and fluid and electrolyte transport in the small intestine of the cat.

The effects of cholera toxin on tissue osmolality and on net transport rates of water, sodium, chloride and potassium as well as on unidirectional fluxes of water and sodium were studied in vivo. In all experiments the toxin caused a net secretion of water, sodium, chloride and potassium. The unidirectional sodium transport from tissue to lumen was increased while the flux in the opposite direction was reduced 180 min after cholera toxin instillation. Cholera toxin produced only a small reduction in the villous tissue hyperosmolality, created by the intestinal countercurrent exchanger. This reduction was far too small to explain the observed net secretion of fluid and solutes induced by the cholera toxin. Other mechanisms underlying the cholera secretion are discussed.