RESUMO
Estrogen regulates reproductive behavior and drives the proliferation and differentiation of several cell types. These physiological functions of estrogen are mediated by estrogen receptors (ERs), and each ER isoform plays a distinct role. To clarify the molecular mechanism of estrogen action and to evaluate the effect of ERs on the secretion of ovalbumin (OVA) in pigeon oviduct epithelial cells (POECs), we determined the complete coding sequences encoding ER alpha (ERα) and ER beta (ERß) in pigeons. The abundance of pigeon ERα and ERß mRNA was detected using quantitative polymerase chain reaction. These results revealed that pigeon ERα is highly expressed in the oviduct, while pigeon ERb is highly expressed in the ovary and kidney. We hypothesize that ERα mRNA predominates over that of ERß in the oviduct. The expression of ERα can be down-regulated by 17ß-estradiol, and the knockdown of ERα promoted OVA mRNA expression in cultured POECs, indicating that ERα may play an important role in OVA secretion.
Assuntos
Células Epiteliais/metabolismo , Receptor alfa de Estrogênio/genética , Receptor beta de Estrogênio/genética , Animais , Clonagem Molecular , Columbidae/genética , Estradiol/metabolismo , Receptor alfa de Estrogênio/biossíntese , Receptor beta de Estrogênio/biossíntese , Feminino , Expressão Gênica , Oviductos/metabolismo , RNA Mensageiro/biossínteseRESUMO
The full-length pigeon ovalbumin (OVA) gene cDNA was cloned and sequenced by reverse transcription-polymerase chain reaction (RT-PCR) and rapid-amplification of cDNA ends. A 386-amino acid protein was predicted for the obtained sequence, which had 67% identity with the chicken protein. Similar to chicken OVA, the pigeon OVA gene is a non-inhibitory serine protease inhibitor. Quantitative PCR analysis revealed that pigeon OVA mRNA was highly expressed in the oviduct, and trace amounts were detected in other tissues. During the reproductive cycle, pigeon oviduct OVA mRNA expression reached its peak during the egg-laying stage, decreased with brooding, and then increased again during the squab-feeding period. Moreover, the relative OVA expression level in pigeon oviduct epithelial cells could be upregulated by a constant concentration of steroid hormones.