Expression of oestrogen receptors alpha and beta and of aromatase in the testis of immature and mature boars.
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The boar testis secretes high amounts of oestrogens. In order to test for a likely local significance, we investigated the expression of oestrogen receptors (ER) in immature and mature boar testes using immunohistochemistry (IHC), in vitro and in situ reverse transcription-polymerase chain reaction (RT-PCR). Samples were from 25 boars castrated at ages of 50, 100, 150, 200 and 250 days. Mouse monoclonal primary antibodies against porcine ERalpha (clone HT227), human ERbeta1 (clone PPG5/10) and human P450 aromatase (clone SM1671P) were used. Expression of the mRNA was tested utilizing primers specific for the respective porcine mRNA sequences. ER immunoreactivity was exclusively localized to the nuclei. In immature boars, 90.6 +/- 1.2% of prespermatogonia and 71.0 +/- 2.6% of the Leydig cells showed a strong staining for ERalpha; 95.5 +/- 3.5% of the prespermatogonia but none of the Leydig and Sertoli cells were ERbeta-positive. In mature boars a strong staining for the ERbeta was observed in virtually all Sertoli, Leydig and germ cells, except for the elongating/ed spermatids, which were clearly negative; for the ERalpha, strong immunoreaction signals were restricted to spermatogonia and primary spermatocytes with 93.6 +/- 2.7% of these cells being positive; distinctly less intensive signals were observed in 51.4 +/- 0.27% of the secondary spermatocytes, round spermatids and Leydig cells. In vitro RT-PCR was positive for both receptors and results of in situ RT-PCR matched those obtained by IHC. P450 aromatase immunoreaction was restricted to the cytoplasm of Leydig cells. These findings suggest that testicular ER may be important factors contributing to onset and maintenance of spermatogenesis in the boar.