On the Effect of the Anterior Pituitary-Like Hormone on the Ovary of the Hypophysectomized Rat

The object of this paper is first to describe the more minute histology of the ovarian changes induced by the removal of the hypophysis, and second to show how the anterior pituitary-like hormone, obtainable from pregnancy urine or placenta (A.P.L.), influences these changes. It has been observed by numerous investigators that removal of the hypophysis inhibits the development of the reproductive system, but it was not possible to study these conditions in an extensive manner until P. E. Smith (1) found a method by which it became possible to remove the pituitary in one of our most common laboratory animals, the rat. In his detailed paper on the effect of hypophysectomy in the rat. Smith stated that the ovary decreases in weight and most of the follicles undergo atresia, but the corpora lutea persist very much longer than under normal conditions. Previous work in this laboratory fully confirmed these findings (2,3), and showed that the corpus luteum of pregnancy remains functional during the second half of gestation if the pituitary has been removed at mid-pregnancy (4). Studies on the effect of A.P.L. on the ovary of the hypophysectomized rat (2, 3, 6) showed that this hormone is unable to induce either the maturation of follicles or the formation of normal or atretic corpora lutea, but it has a very marked influence on the thecal cells which assume, under its action, the appearance of corpus luteum cells. Since the publication of these observations a more intimate study of the underlying histological changes during ovarian atrophy showed that the lack of pituitary hormone, apart from its effect on the follicles and corpora lutea, produces very striking changes in the connective tissue elements of the ovary. Most of the tissues for this study have been fixed in a sublimateformalin mixture, embedded in paraffin and stained with haematoxylineosin. For the demonstration of lipoids, frozen sections have been stained with Sudan III. In 50 sexually mature female rats (three and a half months of age), as early as twelve days after removal of the hypophysis, a special cell type was found to appear in the stroma of the ovary Avhich was very poor in protoplasm and had a round nucleus with the chromatin arranged to form the “wheel figure” so characteristic of the plasma cells or the so-called “Radzellen” of the German histology.