Circadian rhythms in epidermal mitotic activity

Abstract

Circadian variations in mitotic index, mitotic rate (cells entering mitosis per hour) and mitotic duration were investigated in the epidermis of the back and ear of hairless mice. The Colcemid technique was used. In both epidermises the three mitotic parameters fluctuated during day and night. The mitotic index and mitotic rate showed approximately parallel variations. The mitotic duration, however, seemed to vary inversely with the mitotic rate. The variations in the epidermis of the ear and back were not quite parallel. As a rule, low values of mitotic rate were found in the morning and high values during the night.