Aromatase expression in Xenopus oocytes: a three cell-type model for the ovarian estradiol synthesis

Abstract

In contrast to the classical model describing the synthesis of androgens and estrogens as restricted to somatic cells, a previous study demonstrated that Xenopus laevis oocytes participate in androgen synthesis. The objective of our study was to determine whether Xenopus oocytes are also involved in estrogen synthesis. More precisely, we analyzed aromatase expression by in situ hybridization and RT-QPCR and measured aromatase activity. Aromatase, the enzyme responsible for estrogen synthesis, appears to be expressed and active not only in the follicular cells but also in the vitellogenic oocytes. During late oogenesis, aromatase oocyte expression and activity decreased concomitantly with the trend observed in surrounding follicular layers. In order to investigate the role of estradiol-17b (E 2 ), we studied its effect on oocyte meiotic resumption. It appears that, as in Rana pipiens, E 2 inhibited the follicle-enclosed maturation of Xenopus oocytes, likely through inhibition of LH-induced maturation-inducing steroid synthesis. In addition, E 2 exerted a slight enhancing action on denuded oocyte maturation whose biological significance remains unclear. Together, our results demonstrate that Xenopus oocyte significantly participates in ovarian E 2 synthesis and this may be a common feature of vitellogenic vertebrates.

Nanosilver particles increase follicular atresia: Correlation with oxidative stress and aromatization

“…To understand how NSPs impaired angiogenesis, one should consider the crosslink between aromatization, ovarian estrogen level and angiogenesis. To uncover the relation and/or association between the Cyp19 and estrogen, it should be considered that in ovaries key genes that are involved in encoding the aromatase cytochrome p450 are co‐expressed with E 2 , suggesting the E 2 ‐induced paracrine or autocrine impacts . Early studies showed that at the early and late pre‐antral stages, follicles possess by gonadotropins that lead initiating E 2 synthesis .…”

“…To uncover the relation and/or association between the Cyp19 and estrogen, it should be considered that in ovaries key genes that are involved in encoding the aromatase cytochrome p450 are coexpressed with E 2 , suggesting the E 2 -induced paracrine or autocrine impacts. 53,54 Early studies showed that at the early and late pre-antral stages, follicles possess by gonadotropins that lead initiating E 2 synthesis. 30,33 Accordingly, the preovulatory follicle has the highest intrafollicular levels of estradiol, primarily due to the size of its GCs population and its capacity for androgen aromatization.…”

Validation of Electrochemiluminiscence Immunoassay for Ovarian Steroid Determination in Rhinella arenarum

“…The first studies conducted in Rana nigromaculata showed that the levels of steroids secreted by follicles incubated in vitro vary with the size of the follicles. E 2 are produced mainly by medium‐sized follicles, T by medium‐sized follicles, and P 4 by the largest follicles (Kwon et al., ’93, Gohin et al., ). This suggests that the steroidogenic capacity of the follicles changes during their development, from the production of E 2 to that of P 4 .…”

Cyp19a1 (Aromatase) Expression in the Xenopus Brain at Different Developmental Stages

“…The cDNA of Xenopus Vimentin and Neuroβtubulin have been used previously . For in situ cyp19a1 , an IMAGE cDNA clone (ThermoScientific, Wilmington, DE, USA; clone ID, 6944814) was used . Sense and antisense digoxigenin‐labelled riboprobes were transcribed using the Digoxigenin RNA labelling kit in accordance with the manufacturer's instructions (Roche, Mannheim, Germany).…”