Phenol red inhibits uptake of phosphate by the everted gut sacs of mice.

Uptake of phosphate by the everted intestinal sacs of mice was measured at various concentrations of this anion in the incubation medium. Phenol red when added to the serosal side was able to inhibit the uptake of phosphate significantly, while uptake of glucose or proline was unaffected. When para amino hippuric acid was present along with phenol red in the serosal compartment, the inhibition exerted by the dye on phosphate uptake was significantly less. These findings suggest that entry of phenol red into gut tissue from the serosal side interferes with the mucosal uptake of phosphate by the everted intestinal sacs of mice.