Abstract
Although the mammalian colon is thought to absorb large quantities of total ammonia, principally in the form of NH3, quantitative support for this hypothesis is lacking. In rat distal colon, we observed that NH3 was approximately 400 times more permeant than NH+4. In addition, colonic HCO-3 secretion influenced total ammonia (NH3 plus NH+4) absorption; that is, alteration of HCO-3 secretion caused a parallel change in total ammonia absorption. Perfusion with total ammonia also caused net HCO-3 secretion to switch to net absorption, and, in the setting of preexisting HCO-3 absorption, perfusate containing total ammonia enhanced HCO-3 absorption. These events suggest that colonic HCO-3 secretion titrates luminal NH+4 to NH3, permitting NH3 to diffuse from the lumen, while HCO-3 is titrated to carbon dioxide and also diffuses from the lumen. In support of titration of NH+4 and HCO-3, the magnitude of induced HCO-3 absorption approximated total ammonia absorption. This titration relationship suggests that, in kinetic studies, total ammonia absorption will be limited by a fixed rate of HCO-3 secretion. A model was developed that simulated these events.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
