Abstract
One specific physiological phenomenon of Chinese brown frog (Rana dybowskii) is that its oviduct expands prior to hibernation instead of expanding during the breeding period. In this study, we investigated the expression of P450arom and estrogen receptors α and β (ERα and ERβ) in the oviduct of Rana dybowskii during the breeding period and prehibernation. The results of the present study showed that there were significant differences in both oviductal weight and size with values markedly higher in prehibernation than in the breeding period. P450arom was observed in stromal tissue in both the breeding period and prehibernation. ERα was expressed in stromal tissue and epithelial cells in both periods, whereas ERβ could not be detected. The mean protein and mRNA levels of P450arom and ERα were significantly higher in prehibernation as compared to the breeding period. Besides, oviductal content of 17β-estradiol was also higher in prehibernation than in the breeding period. These results suggested that estrogen may play autocrine/paracrine roles mediated by ERα in regulating the oviductal hypertrophy during prehibernation.
Highlights
The female reproductive tract exhibits alterations in structure and function developmentally as well as with seasonal reproductive activity
To extend our understanding of the regulation of oviductal hypertrophy in Rana dybowskii, the present study investigated the expression of P450arom, ERα, and ERβ in the oviduct of Rana dybowskii during the breeding period and prehibernation to elucidate the relationship between estrogen and oviductal hypertrophy during prehibernation
The higher oviductal weight and relative circumference values of the oviduct were observed during prehibernation in October and lower values were found during breeding period in April (Figures 1(e) and 1(f))
Summary
The female reproductive tract exhibits alterations in structure and function developmentally as well as with seasonal reproductive activity. Oviducts respond to hormonal cues from ovaries with tissue proliferation and differentiation in preparation of transporting and fostering gametes [1]. These responses produce oviductal microenvironments conducive to reproductive success [2]. Oviduct, used in the comparative sense meaning structures derived from the embryonic Mullerian duct, responds to endocrine signals through changes in gene expression, protein synthesis, and morphology with sexual maturation and reproductive activity [3, 4]. Sex steroid hormone receptors in the oviduct receive endocrine signals and regulate growth, differentiation, and protein secretion. Ligand binding of oviductal sex steroid hormone receptors results in a positive feedback that elevates expression levels of sex steroid hormone receptors, priming the tissue to receive further signals in general [5]
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