[Seasonal dynamics of cellular mitotic activity in the adenohypophysis and adrenal cortex of normal rats and under the stress reaction].

The experiments have been performed in 162 white non-inbred male rats. The animals are sacrificed on the third week of every month between 11 A. M. and 13 P. M. Some essential changes in the mitotic coefficient (MC) are noted in the organs of the hypophysis-adrenal system during 1 year. In the intact rats adenohypophysis the MC reaches its maximum in March, and in September in drops to its minimal value. In the glomerular and the fascicular-retinal zones of the intact animal adrenal cortex, two periods with an elevated mitotic activity are noted during the annual cycle (in spring and in autumn). Formalin stress produces a decrease in the adenohypophysis, and in the fascicular-retinal zone of the adrenal cortex--an increase of the MC. In the fascicular-retinal zone there is not any reaction only in May and June. Perhaps, the reason is in some seasonal changes of reactivity of the zone mentioned to ACTH. The seasonal dynamics of the MC in the hypophysis-adrenal system organs is in general maintained under the stress.