Effect of age on cell division, ³H-thymidine incorporation, and diurnal rhythm in the lens epithelium of rats

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Abstract

The rapid growth of the rat lens during the first year of life is accompanied by only small changes in the size of the epithelial population. The cell layer adapts to the great expansion of lens surface area by spreading of the cells. Cell proliferation as represented in the mitotic and ³H-labeled cell indices decreases during this period of life. Animals killed in the forenoon showed a reduction of ³H-thymidine incorporation with age which surpassed the fall of mitotic activity. Age-dependent changes in the ratio of labeled cells to mitosis can be explained in part by a shift in the timing of diurnal fluctuations of mitosis in older animals. Variation of ³H-thymidine incorporation associated with the diurnal rhythm in mitotic activity could not be detected with 6 hour sampling intervals