Human corpus luteum: immunocytochemical evidence for presence of prolactin

Six human corpora lutea (day 17-25) of the menstrual cycle and 4 ovarian stromal tissues from 7 cycling women were examined for the presence of the hormone, prolactin, by immunohistochemistry using the indirect peroxidase-antiperoxidase method. After mounting tissue sections of 4 micron, endogenous peroxidases were removed with hydrogen peroxide and the sections were incubated for 1 h at room temperature followed by 16 h at 4 degrees C with a highly specific antisera for human prolactin, nonimmunized normal rabbit serum for a control reaction, or antiserum preadsorbed with excess human prolactin for specificity determination. Following the reaction with the second antibody (goat antirabbit IgG) for 1 h at room temperature, prolactin was localized using peroxidase anti-peroxidase and 3.3'-diaminobenzidine as the chromogen. Prolactin was present and could be localized in the luteal cells of all 6 corpora lutea, but not in any of the ovarian stroma studied. Human adenohypophysis served as a positive tissue control for prolactin immunopositive staining. The localization of immunoreactive prolactin in the corpus luteum demonstrates directly the presence of this hormone in the human ovary, adding further evidence for its role in luteal function.