Chronology of estrogen receptor expression in testes of mouse embryos

Background/aim: To localize and determine the time of expression of estrogen receptors (ERs) in testes of mouse embryos by histology and immunohistochemistry. Materials and methods: Fifty-four mature Swiss-Webster mice (Mus musculus) were used. Group 1 consisted of 34 mature pregnant females, 3 of which were sacrificed every day from 10.5 to 20.5 days postcoitus (dpc). One testis was removed from their embryos and processed for histology and immunohistochemistry. Group 2 consisted of 20 postnatal mice: 5 postpartum (P0) males, 5 males 4 weeks old, 5 males 8 weeks old, and 5 females 4 weeks old. Results: The first nuclear detection of ERs was observed in embryonic male gonads at 11.5 dpc, and a highly significant increase (P < 0.01) was observed at embryonic days 11.5, 13.5, 15.5, 16.5, 17.5, and 19.5, with a peak at 17.5 dpc and continuing to 20.5 dpc. ER expression increased further after birth. Conclusion: Expression of ERs occurred at certain days during mouse embryonic development, indicating the need for estrogen for certain metabolic or morphological events occurring at these days. After birth, estrogen played an important role in proliferation and maturation of certain cells in the testes. Another rise in ER expression occurred during puberty in the mature testis.