The mechanism of action of the uterus on the corpus luteum of the rat is still incompletely understood. Silbiger & Rothchild (1963) suggested that hysterectomy reduced the luteolytic effect of luteinizing hormone (LH) (Rothchild, 1965a) by reducing its secretion, but Christian, Yuan & Rothchild (1968) failed to demonstrate any difference in parameters of LH secretion between intact and hysterectomized pseudopregnant rats. It seemed worth-while, therefore, to test the possibility that the luteolytic action of LH depended on the presence of the uterus.
Regularly cyclic adult Sprague-Dawley rats (200–250 g) were hysterectomized or sham-hysterectomized; a few weeks later, each rat was hypophysectomized and its pituitary transplanted beneath its left kidney capsule. (The corpora lutea, in this preparation, remain functional for several months (Everett, 1956; Rothchild, 1965b).)
Fourteen days later, both the hysterectomized and the sham-hysterectomized rats were divided into two groups: one was injected with 0·9% NaCl solution, the