Cell renewal in noncornified and cornified buccal epithelium in the rabbit

This study was undertaken to compare some aspects of cell renewal in the noncornified and cornified epithelia that are juxtaposed in the buccal mucosa of the rabbit. Specimens were analyzed by autoradiography and scintillation counting at various times after the injection of tritiated thymidine or triated proline. In the noncornified epithelium, the labeling index in the proliferative compartment at 1 hr was 15.5%; in the entire cell population, it was 5.8% at 1 hr, 10.4% at 24 hr, and 20.2% at 72 hr. The leading edge of labeled cells reached the surface by 96 hr. In the cornified epithelium, the labeling index in the proliferative compartment was 8.7% at 1 hr; in the entire nucleated cell population, it was 4.2% at 1 hr, 9.2% at 24 hr, and 12.1% at 96 hr. The leading edge of labeled cells reached the stratum corneum by 96 hr and the surface by 144 hr. It was concluded that renewal occurs at a more rapid rate in the noncornified than in the cornified epithelium under study.