COMPARATIVE STUDY OF LUTEOTROPIN SECRETION BY HYPOPHYSIAL AUTOTRANSPLANTS IN THE RAT. EFFECTS OF SITE AND STAGES OF THE ESTRUS CYCLE1,2

Abstract

The persistence of luteotropin (LTH) secretion in pituitary grafts was studied in 47 rats. In 14 the pars distalis was autografted to the anterior chamber of the eye on the day of estrus. In the 9 animals in which the graft "took," secretion of LTH was demonstrated. When the pars distalis was autografted to the kidney on various days of the cycle (2 animals on the day of estrus, 7 on the second day of diestrus, 9 on the third day of diestrus and 15 in proestrus), secretion of LTH was found in all cases. This was not at first recognizable in the last group, for luteolysis occurs during proestrus and the corpora lutea had lost their capacity to respond. Once new corpora lutea were produced by gonadotropin injection, LTH secretion was demonstrable. In all cases LTH secretion was indirectly measured through the ability of uteri to respond to trauma with a decidual reaction. Despite the fact that no estrogen secretion was evident in the engrafted rats, uteri retained a reactivity to trauma for as long as 42 days. It is concluded that luteotropin is secreted by pituitary grafts regardless of the time of the cycle when the pituitary is transplanted or of the site in which it is placed.