Proliferation decrease in the olfactory epithelium during postnatal development.

Olfactory sensory cells are replaced continuously throughout the life of an animal. In postnatal rats proliferation density decreases dramatically, and continues to decrease into adulthood at least up to 11 months of age. This is true in both the basal cell and supporting cell populations. However, correlation analysis revealed there was no correlation in mitotic rate between the two cell types, suggesting that proliferation of the two cell types is regulated differently. With age, the rat body size and the area covered by olfactory epithelium increases. We present evidence that supporting cell proliferation provides only for growth, whereas proliferation of basal cells provides for both growth and replacement. Further, we present evidence that in older animals the sensory cells live longer than they do in younger animals.