Permeability of the rabbit colon in vitro

The rabbit colon, in vitro as everted sac or diaphragm preparations, exhibits a transmural PD, as high as 70 mV, a short circuit current (SCC) of 100 to 150 μA cm^-2 and a resistance of 300-500 Ω.cm². It maintains these functions for at least 3 h. The SCC can be abolished by amiloride or increased by amphotericin B. Na, Cl, and K flux measurements showed a net influx (mucosa to serosa) of Na and a net efflux of K. The SCC can be accounted for by the movements of these ions. The SCC in the presence of amphotericin B was nearly equivalent to the net Na flux. Amiloride abolished the net Na transfer but did not have a significant effect on the K. The permeability coefficient (Ktransx10⁷) for water was 5,000 cm S^-1 while that for urea was 26 cm s^-1. The rabbit provides a viable preparation for in vitro permeability studies of colonic function and the present observations appear to be consistent with its physiological role.