Hormonally regulated expression of an apocrine epithelial antigen in the cell membranes of endometrial glands.

Abstract

We have raised a rabbit antiserum against formalin-treated membrane glycoproteins isolated by lectin affinity chromatography from human milk fat globules. In immunofluorescence staining the antiserum reacts strongly and exclusively with the apical membrane of the glandular epithelial cells in normal endometrium during the proliferative phase. No membrane-bound antigen is seen during the secretory phase but some positively staining material is found in the glandular lumina and a weak cytoplasmic staining is also seen. The antigen is absent in postmenopausal endometrium but is found in abundance in the cell membrane of the glandular epithelium in endometria from postmenopausal women receiving estrogen treatment. The glandular epithelium of hyperestrogenism-induced endometrial hyperplasia is very strongly decorated by the antiserum. Molecular characterization of the antigen by immunoblotting under reducing conditions reveals two polypeptides of 110,000 daltons and 93,000 daltons from normal endometrium during the proliferative phase. A single band of 75,000 daltons, probably representing shed fragment, is seen in secretory endometrium. This hormonally regulated and strictly located protein differs from many other endometrial proteins in that it is estrogen-induced, while others are dependent on progesterone effect, and it constitutes an interesting histochemical marker of endometrial glands.