Abstract
It has been stated that estrogens are metabolized by the liver of the rat and completely inactivated. The best evidence for this is the excellent work of Heller 1 on tissue slices incubated with various estrogens. Methods of indirect attack in vivo have consisted in attempting to study effects of endogenous or exogenous estrogens in animals in whom the liver had been poisoned. 2 , 3 There have also been attempts to recover estrogens by hashing the whole animal after injection. 4 These have also led to the belief that estrogens are completely inactivated by the liver.
The present study of which this is a preliminary report was undertaken with the view of direct attack on this problem.
The estrogen in question was injected directly into the spleen in 0.05 cc of oil solution. The spleen was exposed through a mid-ventral incision and delivered to the outside; the site of entrance of the needle into the spleen was tied with an encircling silk ligature to prevent leakage of the oil. The injections were made into castrate females primed 14 days previously with 50 γ of estrone. Vaginal smears were taken with a moist, cotton tipped toothpick at 48, 60, and 72 hours after injection, and a fully cornified smear in any one or more of the three periods was considered as positive. These procedures were followed throughout except for a group of 10 animals on 100 γ of estrone, where it was necessary to use 0.1 cc of oil owing to the relative insolubility of the material.
The intrasplenic unit is defined as that amount of estrogen required to produce positive smears in 50% of at least 10 rats treated as described.
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