Regional localization of immunoreactive c-fos and prolactin in human endometrium during the normal menstrual cycle

The objective of the present study was to evaluate the cyclic changes and r egional localization of immunoreactive c-fos and prolactin (PRL) in the hum an endometrium, using immunohistochemistry. Immunoreactive PRL was found in the epithelium of 9.1% of the proliferative specimens and in 55.6% of the secretory specimens (p < 0.05, Fisher's exact test). In the endometrial str oma, immunoreactive PRL was present in 9.1 and 66.7% of the proliferative a nd secretory samples, respectively (p < 0.01). Immunoreactive c-fos predomi nated in the stroma and was identified in 54.5% of the specimens in the pro liferative phase, but in only 7.1% of those in the secretory ph ase (p < 0. 05). The progesterone/estradiol ratio was lower in the patients expressing immunoreactive c-fos (median = 13.1 ng/ml) compared to those who did not (m edian = 84.5 ng/ml, p < 0.05). We conclude that immunoreactive c-fos is fou nd mostly in stromal cells during the proliferative phase of the menstrual cycle, and is sharply reduced during the secretory phase, when the endometr ium is under progesterone stimulation - attested by PRL production.