Comparative views of electrophysiological parameters of large intestinal segments in pig, sheep, pony, guinea pig and rat.

Short circuit current (ISC) and transepithelial conductance (gt) across sheets of epithelia were measured in the caecum, the proximal and the distal colon of pig, sheep, pony, rat and guinea pig. The electrical parameters underline the basic segmental and species differences. The diversity of ISC demonstrates the different nature of electrogenic transport mechanisms, and data clearly show the heterogeneity with respect to transport mechanisms along the large intestine in the various species. The great differences in amiloride sensitive ISC indicate the variabilities in the electrogenic Na transport. Whereas in the pig, sheep and pony caecum, in the guinea pig proximal colon and in all segments of the rat hindgut no indications for a major electrogenic Na transport was seen, in all other segments amiloride caused a marked decrease in ISC. Electrogenic Na transport seems to be highest in sheep distal colon and in pig proximal and distal colon, somewhat less in guinea pig and in pony distal colon. The epithelium with the lowest Powest transepithelial conductance clearly is that of the pony caecum. Except in sheep, gt-values are not much different from those in pony and also pig and guinea pig. By far the epithelium with the highest conductance is that of the rat proximal colon. gt was similar in the proximal and the distal colon of pig, sheep and pony; in guinea pig values were slightly, in rat much lower.