Synthesis and Release of Estrogen- and Progesterone-Dependent Proteins by the Baboon (Papio Anubis) Uterine Endometrium1

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Abstract
This study was undertaken to determine the regulation of stage-specific endometrial proteins of the baboon uterus by estradiol (E2) and progesterone (P). Ovariectomized females were either untreated or treated with E2 for 7 or 14 days, or primed with E2 for 14 days, and then treated with E2 plus P or P alone for 7 or 14 days. Steroids were administered via Silastic capsules and, as determined by radioimmunoassay, physiological levels were present in the peripheral serum of each treatment group. Endometrial tissue obtained after steroid treatment was incubated in the presenceof [35S] methionine for 24 h at 37.degree.C, and the culture medium was analyzed by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) followed by fluorography. Steroid treatment resulted in a doubling of the synthesis and release of labeled macromolecules into culture medium compared to the levels observed in long-term ovariectomized animals, together with the appearance of specific proteins whose synthesis required either E2 or E2 .+-. P. A single protein (Mr 33,000; pI 7.6) was only observed after E2 treatment, and a family of high molecular weight basic proteins (Mr > 200,000) and a group of acidic proteins (Mr 130,000) required both E2 and P. In the absence of E2, P maintained the synthesis and release of three basic proteins (Mr 88,000, 66,000 and 40,000) as well as the other proteins observed in the ovariectomized animals. A comparison of the synthetic pattern in the E2-primed animals treated with either E2 + P or P alone clearly illustrated the synergistic action of E2 + P, thus suggesting an important role for E2 in regulating synthetic events during the early and mid-luteal stages of the menstrual cycle. The identification and characterization of the stage-specific, steroid-induced proteins of the baboon endometrium described in this study will now enable us to attempt to elucidate the functional significance of endometrial proteins in the primate.