Chloride absorption by the rabbit colon occurs under all the experimental conditions tested, even when intraluminal concentrations are lower than the plasmatic ones. In contrast, at caecal levels, chloride absorption rate depends on the experimental conditions. 2. Bicarbonate is always secreted by the colon even for intraluminal concentrations twice the amount of plasmatic ones. At caecal level, it is absorbed only from concentrations similar to those of the plasma or greater. 3. There seems to be an exchange process affecting chloride and bicarbonate at colonic level but not in the caecum.
