Abstract
Nuclear diameter, DNA synthesis, and mitotic index in the pituitary cells of male rats and serum prolactin were measured after a period of 8 days of treatment with a dopamine agonist and an antagonist given with and without estrogen. In the absence of estrogen, the dopamine agonist, bromocriptine, diminished the mean nuclear diameter of the pituitary cells and lowered pituitary DNA synthesis, and the dopamine-blocking agent haloperidol had no effect. Estrogen increased the mean nuclear diameter, pituitary mitotic index, and DNA synthesis. Bromocriptine prevented the estrogen-induced increase in mean nuclear diameter and pituitary DNA synthesis and mitotic index were lowered. Haloperidol augmented the estrogen-induced increase in mean nuclear diameter, pituitary DNA synthesis, and mitotic index. Positive correlations were obtained between mean nuclear diameter and DNA synthesis and serum prolactin. It was concluded that nuclear diameter was influenced by both DNA synthesis and secretory activity in pituitary cells.