Independence of the activation of mucus and potassium secretion on the inhibition of sodium and water absorption by deoxycholate in rat colon.

The dose dependence of the influence of deoxycholic acid (DOC) on fluid and sodium absorption, transmural potential difference (PD), permeability of 14C-erythritol and secretion of potassium and mucus (protein bound hexoses) was measured in the in vivo perfused rat colon. The following results were obtained: 1. The threshold concentration for the inhibitory effect of DOC on fluid and sodium absorption is 2 mmol. In order to decrease PD and increase the colonic permeability for 14C-erythritol the same concentration was needed. 2. In contrast, DOC stimulated potassium and mucus secretion even in a fourfold lower concentration (0.5 mmol). No difference in the responsiveness of the descending and ascending colon was observed. 3. It is concluded that the identical dose dependency of the effect of DOC on fluid and sodium movement, PD, and permeability of the colonic mucosa is consistent with the interpretation that the secretagogue effect of DOC is mediated by an increase in permeability. However, because of their greater sensitivity, mucus and potassium secretion obviously are affected by a different mechanism. It is speculated that mucus and potassium are secreted together by the mucus producing cells of the colonic mucosa under the influence of DOC.