Abstract
Hohlweg's experiment, 1 in which corpus luteum formation was induced in immature “40 to 50 gm. rats” by the administration of single large doses of dihydroxyoestrin benzoate (Progynon-B), constitutes the crucial evidence in support of the currently favored view that oestrogenic hormone stimulates the output of luteinizing hormone by the anterior pituitary. Attempts to duplicate Hohlweg's attractive experiment in this laboratory have unfortunately been unsuccessful. Single subcutaneous doses of as much as 2000 γ of crystalline oestrone (Folliculine-Girard) in oil have been given to each of 10 female rats, weighing from 40 to 50 gm.—this weight corresponding to an age of 24 days in our colony. At autopsy one week later the ovaries of these animals were found to be still immature. There was no histologic evidence of granulosa luteinization. The weights of the ovaries (averaging 12.9 mg. per rat) and of the pituitaries were not significantly altered in comparison with those of uninjected control rats. Barring any theoretical difference in the biologic activity of oestrone and dihydroxyoestrin benzoate, the conflicting results may be due to differences in age-weight relationships in the two colonies. In this connection, Selye et al. 2 have already indicated that the effects of massive oestrogenic hormone doses in rats are first observed with regularity at or near puberty, irrespective of the absolute weight of the test animal.
In order to examine the question further the oestric rabbit was thought to be a desirable test object. As the rabbit exhibits no spontaneous ovulatory cycle, adult does of this species which have been well fed and isolated for 3 or more weeks should, in the majority of instances, have ovaries free of functioning corpora lutea and containing numerous growing and mature follicles.
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