Changes in protein secretion by rat submandibular salivary glands after enlargement caused by repeated amputation of the lower incisor teeth.

The lower incisors of male rats were repeatedly amputated at 3- or 4-day intervals for about 1 month. Four days after the last amputation, submandibular saliva was collected from the anaesthetized rats by intra-oral cannulation, using methoxamine (6 mg/kg), an α-adrenomimetic drug, as an acute secretory stimulus. The rats showed enlarged submandibular and sublingual glands and the protein concentration was significantly less in submandibular saliva than in controls. The types of protein secreted by the rat submandibular gland in response to methoxamine normally differ from those secreted in response to isoprenaline. In the enlarged glands, methoxamine stimulation caused the secretion of proteins similar, by polyacrylamide gel electrophoresis, to those normally secreted in response to isoprenaline, suggesting that repeated lower incisor amputation had caused the glands to lose their normal responsiveness to α-adrenergic agonists. An abnormal protein was also secreted, identical electrophoretically and immunologically with one secreted by the enlarged submandibular glands of rats exposed to chronic isoprenaline administration.