A group of 39 rats underwent excision of the submandibular and sublingual glands and ligation of the parotid ducts through the midventral incision of the neck, while the control group (41 rats) underwent a sham operation. All rats were administered 4NQO in a final concentration of 0.001% in drinking water. At 7, 14, 22 and 28 weeks after administering 4NQO, both groups of rats were killed and their tongues dissected, inspected and then fixed in 10% buffered formalin for histopathological examination. Clinical examination during the first 14 weeks revealed that rats in both groups looked healthy and no differences in body weight were noticed. Afterwards, the average weight gain of the desalivated rats was lower than in the control group (P < 0.01). The number of macroscopic oral lesions increased with time in both groups. However, in the desalivated rats, the first identifiable lesions were seen as early as week 7, whereas in the control group macroscopic lesions were seen only after 22 weeks. Histological examination revealed more affected rats in the desalivated group in the first 14 weeks after administering the carcinogen; lesions showed more severe pathological changes including two cases with evidence of squamous cell carcinoma. The differences between the desalivated groups and control decreased after 22 weeks with almost no differences at the end of the experiment.
- 4NQO tongue cancer