Abstract
It has been stated (see, for example, Sex and Internal Secretions, edited by E. Allen, 1932, p. 528) that the corpus luteum hormone, progestin, does not cause active proliferation with mitotic division in the endometrium, the proliferation observed after ovulation being ascribed to the action of oestrin and not progestin.
Examination of a cross section of the rabbit's uterus after injection of the castrated animal with progestin for five days, as in the usual method of assay, reveals very little evidence of mitotic division; it is, no doubt, this observation which has given rise to the conclusion that progestin does not induce cell division. The great increase, however, in extent of the surface epithelium and gland cells which is seen in the sections, obviously depending upon an increase in the total number of cells, suggests that cell-division has in some way been induced.
In the course of the experiments reported by Makepeace, Corner and Allen 1 it was noted that the uteri of animals examined after 3 days of progestin treatment showed frequent mitoses in the epithelium. Probably, therefore, when the injections of progesterone are continued for 5 days, as in the experiments of other workers, the endometrium passes beyond the division stage, and by the time of autopsy all of the mitotic figures have disappeared.
The following experiment was done to test this conjecture under controlled conditions. Complete oöphorectomies were done on 6 rabbits. At the time of operation, a specimen was removed from the middle of one horn of each uterus as a control. Two of the rabbits each received daily for 3 days 0.5 mg. progesterone (crystalline progestin), an amount comparable with that produced in a rabbit with active corpora lutea.
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