DNA synthesis in the anterior pituitary of the male rat: effect of castration and photoperiod.

Castration increased incorporation of tritiated thymidine into total DNA in the anterior pituitary gland. Furthermore, there was a threefold increase in the percentage of labeled basophils 1 month after castration. Exposure of rats to constant light or dark also changed DNA synthesis; these changes depended on age of the animal and on exposure length. The results reflect physiologically induced mitotic activity in specific classes of pituitary cells and further suggest that neuroendocrine mechanisms may be involved in control of cell turnover in the gland.