Some Hormones Involved in Elaboration or Activation of the Mammary Spreading Factor. ∗

Abstract

Summary

1. Hormones which stimulate mammary gland growth cause elaboration or activation of the mammary gland spreading factor. 2. Increasing amounts of estradiol benzoate caused increasing amounts of the spreading factor to be elaborated or activated in the mammary glands of castrate animals, but little or no spreading factor was found to be present in the mammary gland extracts of estradiol-benzoate treated, castrate-adrenal-ectomized animals. 3. Increased amounts of progesterone alone caused increased production of the spreading factor, however, the largest amount of progesterone employed did not give as good response as half the level of progesterone plus a little estrogen. 4. Best elaboration or activation of the spreading factor in response to treatment was with a combination of 1 μg estradiol benzoate and 5 mg progesterone. Other combinations of estrogen and progesterone gave graded responses. The castrate-adrenalectomized animals showed as good production of the spreading factor in response to estradiol benzoate-progesterone as castrate animals. 5. An anterior pituitary extract alone produced only fair amounts of the mammary spreading factor. When a low level of estrogen was added much better response was obtained. 6. One mg level of testosterone caused production of fair amounts of the spreading factor. However, the estrogen-progesterone combination gave a better response. 7. Ten days' treatment with some combinations of hormones caused as much elaboration or activation of the mammary gland spreading factor as was extracted from rats pregnant 10 days.