In vitro protein production by the human endometrium

Protein secretion by the human endometrium was studied in vitro in medium after incubation of tissue minces (n = 10) or glands isolated by collagenase digestion (n = 4) from tissues obtained at the time of curettage from normal women. Samples were incubated in a serum-free medium for 24 h at 38 degrees C in the presence of radiolabeled methionine. Dialyzed medium from each sample was subjected to two-dimensional gel separation, and detected by protein staining. Although 5 of the 27 proteins were considered to be present in the labeling experiments by only one of the three observers, there was agreement about the presence of the 22 others. In addition, the observers categorized the proteins into three groups for purposes of analysis: a) those associated with the follicular phase of the cycle; b) those associated with the luteal phase; and c) those not cycle-related. One protein triplet, labeled #27, showed a significant relation to the luteal phase (p less than 0.01). A complete lack of similarity between the pattern of labeled proteins obtained from the medium and labeled proteins obtained from lysates of cells incubated in the same experiments makes it unlikely that cellular lysis, as opposed to secretion, contributed to the pattern of proteins studied in these experiments.