Immunoreactive β-endorphin in human ovaries

Beta-endorphin (β-EP) immunostainable cells were demonstrated in human ovarian tissue using a non-cross-reacting anti-β-EP serum and the avidin-biotin-peroxidase detection technique. In ovaries from ovulating and premenopausal women, β-EP immunoreactivity was localized in the luteinized cells of theca interna of maturing follicles with almost negligible staining in granulosa cells; cells of primary follicles did not stain. In corpora lutea, luteinized cells in both theca interna and granulosa, layers were equally positive. In postmenopausal ovaries, staining was detectable only in scattered luteinized stromal cells. This is the first report on the presence of immunoreactive β-EP in human ovaries, in which β-EP seems to be produced by the same sex cord cells engaged in active steroidogenesis and may be under gonadotropin central regulation. The significance of this finding is discussed.