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Comparison of Macromolecular Binding of Estradiol in Hormone-dependent and Hormone-independent Rat Mammary Carcinoma¹

Department of Physiology and Medicine, The University of Texas Medical School at San Antonio, San Antonio, Texas 78229

In rat mammary carcinoma, 2 types of cytoplasmic estradiol-binding sites, A and B, are present. The A sites are excluded on Sephade x G-100 chromatography, sediment at 8 S and 4 S in a low-ionic-strength sucrose gradient or at 4 S alone in a high-ionic-strength sucrose gradient, and form an insoluble complex with protamine sulfate. They have a very high affinity for estradiol (K_d 1.2 x 10^-10 M) and do not bind nonestrogenic steroids. The B sites are not seen on Sephadex G-100 chromatography, sediment at 4 S in a sucrose gradient, do not interact with protamine sulfate, and exhibit much weaker binding (K_d 1 x 10^-7 M) than the A sites. Only hormone-dependent tumors exhibit the highly specific A sites, while B sites are present in both hormone-dependent and autonomous tumors. Specific binding of estradiol within the nucleus is confined to hormone-dependent tumors.

¹ This work was supported in part by USPHS Grant CA 11378 and American Cancer Society Grant T-510.

Received 3/23/71. Accepted 5/28/71.

This article has been cited by other articles:

				W. L. Mcguire, K. Huff, A. Jennings, and G. C. Chamness Mammary Carcinoma: A Specific Biochemical Defect in Autonomous Tumors Science, January 21, 1972; 175(4019): 335 - 336. [Abstract] [PDF]