DNA Metabolism of the Mouse Submandibular Gland

¹ Department of Oral Pathology, Loyola University School of Dentistry, Chicago, Illinois

CAF-1 mice, 200 days old, were injected with tritiated thymidine (specific activity, 1.9 c/mmole) at a dose rate of 1 µc/gm body weight. The animals were sacrificed at intervals of 15, 30, and 45 minutes; 1, 2, 4, 12, 24, 42, 44, 46, and 48 hours. The submandibular glands were removed. Autoradiographs of Feulgen sections were prepared.

All acinar cells in 20 oil-immersion fields were counted and the percentages of labeled cells determined. At 1 hour, 0.34 per cent of the acinar cells was labeled. However, between 4 and 12 hours, the labeled cells rose to 0.74 per cent, indicating mitotic division had occurred. The percentage of labeled cells remained on a plateau at 0.74 per cent through 48 hours. The low number of labeled cells and the relatively long interphase showed that the submandibular acinar cells maintained a low rate of turnover in the mouse.