Adrenal cortex of rat: diurnal variation of nuclear volumes and mitotic index of cells in zona fasciculata.

Diurnal variation in nuclear volumes of cells in the adrenal zona fasciculata was observed in adult male Wistar rats (200-230 g) with a peak level at 24.00-03.00 and the lowest level at 09.00. There was found a diurnal variation in mitotic index with a peak value at 06.00-09.00 and a trough at 18.00-24.00.