The electrophysiology of rabbit descending colon. II. Current-voltage relations of the apical membrane, the basolateral membrane, and the parallel pathways.

Abstract

In this paper we employ the data described in the previous paper (I) to derive the current-voltage (I-V) relations of the basolateral membrane, the amiloride-insensitive "leak" pathway across the apical membrane, and the parallel pathways across rabbit descending colon. The results indicated that: a) The resistance of the basolateral membrane is independent of the electrical potential difference across that barrier over the range -8 to 67 mV and averaged 195 omega cm2. The electromotive force across this barrier averaged 50 mV under control conditions and 48 mV in the presence of amiloride. The origin of this difference is discussed. b) The resistance of the parallel pathways averaged 351 omegacm2 and was independent of the transepithelial electrical potential difference over the range -170 to + 90mV. The conductance of these pathways can be reasonably well accounted for by the partial ionic conductances of Na, K and Cl reported previously. c) The resistance of the amiloride-insensitive pathway across the apical membrane averaged 1667 omegacm2 and the electromotive force across this pathway averaged -51 mV. These values are in excellent agreement with those determined by others. The ionic nature of this "leak" pathway remains to be elucidated.