HISTOCHEMICAL AND ELECTRON MICROSCOPY STUDIES OF DENTIN IN TRYPTOPHAN-DEFICIENT RATS

¹ Department of Anatomy, School of Medicine and Department of Biochemistry and Nutrition, School of Dentistry, University of Southern California, Los Angeles, Calif.

In the present investigation histological sections of the incisors from control and tryptophan-deficient rats were treated by various histochemical methods and electron microscopy in an effort to detect changes in the dentin that would explain the failure of this tissue to calcify in the absence of tryptophan. The results of the staining reaction, employing the periodic acid-Schiff method, toluidin blue, and Gomori's method, indicated that the ground substance was in a depolymerized state due to the absence of tryptophan, thus preventing normal calcification of the dentin to take place.

Electron microscopy studies of the dentin from the control and from tryptophan-deficient animals showed morphological differences. In the deficient animals the orientation of the collagen fibrils of 640 A. spacings in the dentin were visible whereas in the normal dentin these fibrils were masked by the unaltered ground substance.

Pepsin hydrolysis of control incisal sections resulted in the enhancing of the staining intensity of the ground substance to both toluidin blue and periodic acid-Schiff reaction. These histochemical changes were similar to those found in the experimental animals.