Mitotic rates in the oral and gingival epithelium of the rat

Abstract

The mitotic rates of the oral epithelium were studied over a 24 hr period by injecting 0.1 mg/100g body weight of colchicine into 16 rats. The rats were divided into four groups so that diurnal variations could be observed. The hard palate, cheek and crevicular gingiva had daily mitotic rates of 6.76, 7.25 and 6.21 per cent respectively. The attached gingiva had the lowest daily mitotic rate of 2.27 per cent, suggesting that it was not as much under the influence of function as the hard palate and cheek. The epithelial cuff showed the highest daily mitotic rate of all the epithelia examined being 9.50 per cent. This suggests that it is an active and functioning tissue and not degenerating. Because it is non-keratinized there may be a need for rapid cell renewal in this area. A diurnal variation was observed in all the tissues examined with the exception of the crevicular epithelium. The overall average area mitotic rates showed a low activity in the evening between 16.00 and 20.00 hours, and a peak between 04.00 and 10.00 hours. The crestal gingiva and the attached gingiva show the lowest mitotic activity at a later time, 22.00–04.00 hours with their peak during the day at 10.00–16.00 hours.