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Progesterone Binding by Normal and Abnormal Human Endometrium

Vincent Memorial Hospital (Gynecological Service of Massachusetts General Hospital), Department of Surgery, Massachusetts General Hospital, and Harvard Medical School Boston, Mass. 02114

Cytosols from 75 normal, 36 abnormal, and 5 decidual human endometrial tissue specimens were assayed for the presence of a high affinity, progesterone-specific binding protein. Thirty of the normal and 15 of the abnormal samples were found to contain a binder which would form a high-affinity complex with progesterone but not with cortisol, 17β-estradiol, testosterone, or 5-androstane-3,-17-dione. Incubation of cytosol with trypsin or incubation for 2 hours at 37 C abolished [³H]progesterone binding by these preparations, indicating the protein nature and heat-lability of the binder. The average equilibrium constant of dissociation, Kd, of the progesterone-binder complex was 4.0 x 10^–10M in each phase of the menstrual cycle. The concentration of the binder varied over the cycle, however, with a significant peak at mid-cycle (P = .02). The average saturation values in femtomoles (fmoles)/mg protein ranged from 21 in the early proliferative phase to 64 in the late proliferative samples, dropping to 36 in early secretory and to 3 in the late secretory phase of the cycle. No progesterone-specific binding was detected in decidual samples. Saturable binding was demonstrable in 10 of 22 endometrial hyperplasias, 80–1840 fmoles/mg protein, with high affinity, Kd 3.3 x 10^–10M. Two other hyperplasia samples bound progesterone, but with lower affinity. Two grade I adenocarcinomas, one grade III adenosquamous carcinoma, and one grade III adenocarcinoma contained the progesterone binder, but in 9 other cancers no detectable binder was present. A benign adenocanthomyoma was found to contain a progesterone binder (18 fmoles/mg protein with a Kd of 2.5 x 10^–10M).

Supported by USPHS Grant CA 12903.

This paper was presented in part at the Fourth International Congress on Hormonal Steroids, Mexico City, September, 1974.

Received May 8, 1975.