Tissue-specific expression pattern of estrogen receptors (ER): Quantification of ER alpha and ER beta mRNA with real-time RT-PCR

We have examined the tissue-specific mRNA expression of ERa and ERP in vari ous bovine tissues using real-time RT-PCR. The goal of this study was to ev aluate the deviating tissue sensitivities and the influence of the estrogen ic active preparation RALGRO on the tissue-specific expression and regulati on of both ER subtypes. RALCRO contains Zeranol (alpha -Zearalanol), a deri vative of the mycotoxin Zearalenon, shows strong estrogenic and anabolic ef fects, and exhibits all symptoms of hyperestrogenism, in particular reprodu ctive and developmental disorders. Eight heifers were treated over 8 weeks with multiple-dose implantations (0x, 1x, 3x, 10x) of Zeranol. Plasma Zeran ol concentration, measured by enzyme immunoassay, of multiple treated heife rs was elevated. To quantify ERa and ERP transcripts also in low-abundant t issues, sensitive and reliable real-time RT-PCR quantification methods were developed and validated on the LightCycler. Expression results indicate th e existence of both ER subtypes in all 15 investigated tissues. All tissues exhibited a specific ERa and ERP expression pattern and regulation. With i ncreasing Zeranol concentrations, a significant downregulation of ERa mRNA expression could be observed in jejunum (p <0.001) and kidney medulla (p <0 .05). These data support the hypothesis that ERP may have different biologi cal functions than ERa, especially in kidney and jejunum.