Alterations in the Percentage of Cell Types in the Hypophysis by Gonad Transplantation in the Rat1

An ovarian graft in the male rat, normal or castrated after puberty, produces only follicles, while both follicular development and luteinization occur in an ovary grafted into a female (1, 2). This has been interpreted on the basis of a physiological difference in the pituitaries of the two sexes (2). Cytological differences between the hypophyses of male and female rats were reported simultaneously by McQueen-Williams (3) and Wolfe and Ellison (4). When Pfeiffer (2) observed that the ovaries of females produced only follicles if testes had been grafted into the female at birth, he attributed this to an altered (masculinized) pituitary. Also ovaries transplanted at any time into rats castrated at birth, either male or female, produce both follicles and corpora lutea; but if a testis is present in the prepubertal period, only follicles are produced. This indicates an undifferentiated pituitary at birth which will differentiate according to the gonad present. The testis dominates this differentiation if both a testis and an ovary are present in the same individual. All the above statements regarding the alteration of the pituitary are based upon physiological reactions. Therefore, the present investigation was undertaken in an attempt to correlate these physiological actions with the cytology of the pituitary and to demonstrate whether a pituitary which is experimentally altered in its physiological reactions shows corresponding changes in cell types.