Morphometric investigations on endocrine glands. VI. Changes in rat pituitary glands after ovarectomy and a single injection of estradiol benzoate once per cycle period.

The application of 0.7 microgram estradiol benzoate to ovarectomized rats twice a week (about once per cycle period) causes a return of pituitary weight to values comparable with untreated animals. In contrast, such dosages are ineffective to suppress the enlargement of gonadotropic cells after ovarectomy. After gonadectomy of rats an increase is observed both in number and in volume of the so-called gonadotropic (PAS-positive, alcian blue-negative) cells in their pituitary glands. Natural or synthetic steroidal compounds with estrogenic, androgenic or gestagenic effects may prevent or reduce such changes (review Kramer et al. 1968). Analogous results are seen after administration of the non-steroidal methallibure (Paget et al. 1961). A daily unit dose of 0.5 microgram estradiol seems to be sufficient (Hohlweg and Dohrn 1932; review Romeis 1940). The estrogen level is a function of cycle stage with maximum and minimum, therefore it should be tested, whether or not a single injection of an equal dose will inhibit the development of castration cells.