ULTRASTRUCTURE OF PITUITARY LACTOTROPIC CELLS OF OESTROGEN TREATED MALE RATS

Pituitaries of intact and gonadectomized male rats, treated with 50, 100 and 500 μg of oestrogen dipropionate every second day, were examined 15, 30 and 60 days after the beginning of the experiment. The following results have been obtained: 1. The differentiation of the chromophobes into LTH cells is regularly preceeded by a number of cell divisions. Mitosis was also noted in LTH and STH cells; hyperplasia is most pronounced during the first two weeks of treatment and later is no longer proportional to the doses and duration of treatment. 2. In the large chromophobic and LTH cells synthetic and suppressive processes are described: a)Synthetic processes predominate in most of the cells during the first two weeks. Variability in the quantity of polysomes and granular endoplasmic reticulum is expressed in relation to the doses and the duration of the experiment; prolongation of the treatment with higher doses induces alterations in the appearance of polysomes and the endoplasmic reticulum. b)Suppressive processes become more evident in the chromophobic and LTH cells with prolongation of treatment. They are characterized by regression of the nucleolus, dissolution of the granular endoplasmic reticulum and other cytoplasmic components, and by heterogenity of bodies of the lysosomal system. In intact and castrated male rats oestrogen stimulates synthetic processes in the pituitary cells leading to the differentiation of LTH cells. It seems that chromophobic cells are the most sensitive, but the influence on the STH and other pituitary cells is significant. © 1969 Springer-Verlag.