Human Uterine Luminal Fluid Proteins Associated with Secretory Phase Endometrium: Progesterone-Induced Products?1

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Abstract
Molecular sieve chromatography over Sephadex G-200 columns of human uterine washings from patients in the secretory phase of the menstrual cycle revealed the presence of a protein peak that was absent from serum and, with 1 exception, was not found in similarly treated washes of proliferative endometria. Ten of 11 secretory washes contained this material, whereas it could not be demonstrated in 7 of 8 of the proliferative washes and each of 2 washes of inactive endometria. None of the 9 sera obtained simultaneously (4 proliferative, 4 secretory, and 1 inactive) contained this protein peak. This secretory-phase-specific material contained 1 major and several minor bands of stained protein on polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The major protein fraction could also be stained with the periodic acid-Schiff reagent, suggesting its glycoprotein nature. The possibility that these proteins are secreted into the lumen of the uterus as a direct result of progesterone action on this tissue is currently under investigation.