Segmental differences in K-transport across rabbit proximal and distal colon in vivo and in vitro.

Net K-transport was investigated in three different segments of rabbit proximal and distal colon. In vivo studies used a dialysis method, and in vitro studies an everted sac preparation. Results from both methods are in good agreement and show net K-absorption in the two segments of the proximal colon, and net K-secretion in the distal colon. K-absorption in the proximal colon seems to be an active mechanism, because K is transported against an electrical potential gradient. The present study is a comparative approach to demonstrate the heterogeneity of an organ function, and represents the first direct comparison of K-transport in various segments of rabbit colon under in vitro and in vivo conditions.