Weight of Pituitary and Thyroid of the Rat at Various Stages of the Oestrus Cycle

Abstract

In the recent literature on the relation of the pituitary gland to reproduction there have been several notes concerning changes in the histological picture or in the physiological activity of the pituitary associated with changes in the oestrus cycle. Charipper and Haterius 1 observed an increase in the size and number of the basophils during oestrus, although the cells were not counted or measured. Wolfe and Cleveland 2 found an increase in the eosinophilic cells during oestrus and an increase in granules in the basophilic cells during late dioestrus. Smith and Engle 3 found an increase in the gonad-stimulating hormone of the anterior pituitary during dioestrus as tested by the implant method. Wolfe 4 confirmed this.

The observations presented here were made on mature normal female rats ranging from 3 to 6 months in age. Infected animals and animals having irregular oestrus cycles or cycles over 6 days in length were excluded.

Animals of the same strain were kept under the conditions and on the diet described previously. 5 , 6 Vaginal smears were made at intervals of 12 hours or, in most cases, of 8 hours, and oestrus was defined as the period at which an abundance of cornified cells was obtained, after the preceding smear had shown nucleated epithelial cells. Dioestrus was defined as 48 or more hours after this time. Three animals with very regular cycles were killed 20 hours before the expected onset of the next oestrus. The animals were killed with chloroform and the pituitary, thyroid and adrenal were quickly removed and weighed in a closed weighing bottle to 0.1 mg. The data on the adrenal have been previously reported. 6