THE RESPONSE OF ADULT RAT ORAL TISSUES TO PROTEIN DEPLETION: HISTOLOGIC OBSERVATIONS AND NITROGEN ANALYSIS

¹ Bureau of Biological Research, Rutgers University, New Brunswick, N. J., and The Special Dental Research Project, VA Hospital, Brooklyn 9, N. Y.

A study has been made of the responses of oral tissues of large, adult, male rats to protein depletion during a 63-day period. Histologic changes were compared and correlated with organ weight and nitrogen content changes. The oral structures studied were submaxillary and sublingual glands, mandible, and tongue (histologic study only). The responses of these structures were compared with those of heart, liver, and kidney.

Results were as follows:

1. Weight Changes. (a) Protein-depleted animals weighed 46 per cent less than ad libitum-fed control animals. Food restriction, caused by depletion, accounted for only 7 per cent of this difference, as shown by pair-fed controls. (b) All organs studied weighed less in depleted animals than in controls, with the exception of liver. Greatest weight loss occurred in the salivary glands.

2. Nitrogen Content. Although organs from depleted animals were smaller and contained less total nitrogen than organs from controls, the per cent nitrogen content was the same in all tissues of all groups, with the exception of liver. Livers from depleted animals weighed approximately the same as livers from controls, and had less nitrogen and more fat than control livers.

3. Histology. (a) Sections through the lower first molar and its periodontium revealed marked osteoporosis in all groups of animals. (b) The salivary gland acini and ducts were smaller in depleted animals than in controls. Spaces, indicative of edema, were seen between borders of adjacent acini. (c) The tongue changes were of a mild atrophic nature and affected epithelial thickness, papillae, and glands of the tongue. (d) The histologic appearance of heart and kidney was unchanged in depleted animals, while liver of depleted animals showed an extensive fatty metamorphosis.