The purpose of this study was to evaluate the effects of excisional wounding, tobacco tar, and removal of submandibular gland on the carcinogenesis induced by DMBA application of the tongue in Sprague-Dawley rats.
Seventy-seven rats were divided into experimental group and control group(group 6), and experimental group is subdivided into five group. In group 1, the lateral border of middle third of the tongue was painted 3 times weekly with DMBA. In group 2, the same portion as above was painted with DMBA and proceeded one time weekly by excised with scissor. In group 3, the same portion as above was painted with DMBA and tar. In group 4, the same portion as above was painted with DMBA and tar, and proceeded excisional wounding in the lateral border of tongue. In group 5, the same portion as above was painted with DMBA and tar, and proceeded excisional wounding in the lateral border of tongue after removal of submandibular gland. In group 6, none was treated.
At each 5,10,13,16 and 20 weeks after experiment, 2 animals in the each group 1,2,3,4, and 5, and 2 animals in the group 6 were sacrificed with ether, and then formalin-fixed paraffin-embedded sections were stained as H-E staining rountinely, Masson´s trichrome staining for collagen fibers, and PAS staining for glycogen.
The obtained results were as follows ;
1. In group 1,hyperkeratosis and hyperplasia at 5-10 weeks, and epithelial dysplasia at 16-weeks, carcinoma in situ at 20 weeks were observed, and in group 2 carcinogenesis was progressed more repidly than that of group 1 or group 3.
2. In group 4, carcinogenesis was progressed more repidly than that of group 2. In group 5, carcinoma in situ at 10-13 weeks, highly differentiated squarnous cell carcinoma at 16 weeks, and well differentiated squamous cell carcinoma at 20 weeks were onserved.
3. The chronic inflammatory response in the underlying connective tissue were observed and minor salivary glands were changed into pleomorphic or cystic degeneration, and in some portion, neuromatous proliferation was observed.
4. In group 4, carcinogenesis was observed predominantly in the lateral border of the tongue and faintly in entire mucosa of the tongue in some animals.
In experimental chemical carcinogenesis of tongue in rats, we could find that excisional wounding accelerated the process of carinogenesis, and more rapidly progressed under the condition of xerostomia by proceeding application of DMBA and tar after sialadenectomy.
|