Phenol red as volume marker in rat stomach with mucosal damage

Phenol red, long considered an acceptable volume marker in gastrointestinal experiments, has been tested in rat stomach damaged by exposure to aspirin. Significantly more phenol red was lost from stomachs damaged by aspirin than from control stomachs. Phenol red, therefore, should not be used as a volume marker in damaged stomachs. Volumes of fluid in the stomachs, which increased during the experiment, were calculated from inulin concentrations. Changes in volume of stomach fluid in experimental animals were not significantly different from those in controls.