Influence of pH on intestinal fluoride transport in vitro.

The effect of pH on intestinal fluoride (F) absorption was investigated in vitro using isolated segments of dog jejunum in a 2-chamber system. The pH of the mucosal buffer was varied in the range 6.5-8.2, and F concentration in the range 0.11-1.1 mM (2.1-21 ppm F). The serosal buffer was held constant at pH 7.5. No effect of pH within this physiological range was observed on F transport across the intestinal segment. Much lower pH values on the mucosal side inhibited F transport, but this appeared to be secondary to toxic effects on the epithelium, including an inhibition of water transport. Within the range tested, no evidence was found supporting the concept that F transport across intestinal epithelium occurs as the undissociated hydrogen fluoride (HF).