[Circadian rhythm of proliferative processes in the sebaceous glands]

The proliferation process indices (such as the mitotic activity 0/00,labelled cell 0/00 and the amount of mitoses arrested by colchicine 0/00) were studied in two sebaceous glands of rats-the gland of the external auditory meatus and the tarsal sebaceous gland. It was established that the diurnal changes of the number of mitotically dividing cells and the DNA synthesizing cells could be presented as one-peak curves, the maximum falling on the night and morning hours and the minimum-on the day-time and evening. The average diurnal mitotic activity in terminal portions was 16, 3-1, 9 and the average amount of labelled cells was 76, 9-6, 1. In the excretory ducts they were 13, 0-1,6 and 65, 6-5, 4 respectively. The amount of C-mitoses in rats which were given colchicine was 75, 7-5,1 in the morning hours and 58, 1-4, 5% in the evening hours. It permitted to calculate the duration of mitoses which were equal to 1, 9 hour in the morning and 1,2 hour in day-time.