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November 1977

Breast Cancer: Physiological Mechanisms of Steroid Hormone Action as a Guide to Therapy

Author Affiliations

From the Division of Research, Alton Ochsner Medical Foundation, New Orleans.

Arch Intern Med. 1977;137(11):1603-1604. doi:10.1001/archinte.1977.03630230077020

In recent years, it has become apparent that the physiological activities of steroid hormones are mediated by their entrance into the cell cytoplasm by diffusion or active transport and by their being bound to specific high affinity-low capacity, proteinaceous receptors (Figure). The receptor is probably altered in its conformation on joining with the steroid, and the receptor-steroid complexes are then activated before being transported into the nucleus. Depending on the steroid and receptor involved, either the steroid, the receptor, both, or neither may be altered on translocation to the nucleus. Based on very complete data from the progesterone receptor (progestophilin) of the chick oviduct, the receptor is composed of an A portion (molecular weight [mol wt], 110,000) and a B portion (mol wt, 115,000). One molecule of each portion joins with one molecule of the steroid, in this case, progesterone. The A fragment with its attached progesterone binds to the

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