Steroid-induced proteins in human endometrium

The synthesis of soluble proteins in human endometria at various phases of menstrual cycle was evaluated by polyacrylamide gel electrophoresis of [35S]methionine-labeled proteins. Densitometric analysis of the gels revealed alterations in the rate of synthesis of single protein bands throughout the cycle. Administration of conjugated estrogens (Premarin) to women undergoing hysterectomy, or exposure, in vitro, of the endometrial tissue to 17 beta-estradiol produced an increased incorporation of [35S]methionine into a specific protein which migrated on SDS-polyacrylamide gels at a molecular weight of about 55 000. Induction of this protein was observed only in those endometria showing a secretory histological appearance. The protein was resolved into at least 2 different spots in two-dimensional gel electrophoresis. An increase in the rate of synthesis of another endometrial protein with an apparent molecular weight of 51 000 was observed in tissues exposed in vitro to medroxyprogesterone acetate. These steroid-induced proteins may be a useful marker for studying hormone action in both normal and neoplastic endometria.