Sex steroid receptors in the ovarian follicles of the lizard Sceloporus torquatus

Abstract

Summary Estradiol and progesterone have been recognized as important mediators of reproductive events in the female mainly via binding to their receptors. This study aimed to characterize the immunolocalization of the estrogen receptor alfa (ERα), estrogen receptor beta (ERβ) and progesterone receptor (PR) in the ovarian follicles of the lizard Sceloporus torquatus. The localization of steroid receptors has a spatio-temporal pattern that depends on the stage of follicular development. The immunostaining intensity of the three receptors was high in the pyriform cells and the cortex of the oocyte of previtellogenic follicles. During the vitellogenic phase, the granulosa and theca immunostaining was intense even with the modification of the follicular layer. In the preovulatory follicles, the receptors were found in yolk and additionally, ERα was also located in the theca. These observations suggest a role for sex steroids in regulating follicular development in lizards, like other vertebrates.

Immunolocalization of activin and inhibin at different stages of follicular development in the lizard Sceloporus torquatus

“…In the preovulatory phase, the small cells, cortex, and blood vessels showed marks that may reflect their role in steroidogenesis [ 10 , 52 ]. The registered peak of estradiol concentrations with the onset of ovulation in this species confirms this fact [ 28 , 32 ]. In the hen, the increase of activin is related to the selection of preovulatory follicles to ovulate [ 53 ], and in lizards, it may have a similar function by increasing receptor appearance [ 54 ].…”

“…Also, the localization of each factor is related to the stage of follicular development where they participate in female reproductive physiology at different levels [ 10 ]. The participation of the granulosa layer in follicular development is corroborated by the presence of Act, Inh, and other intraovarian factors such as gonadotropin releasing-hormone (GnRH), gonadotropin release inhibitory hormone (GnIH), bradykinin [ 41 ], sex steroid receptors [ 32 , 42 , 43 ], SCF, C-kit [ 33 ], and its receptors in lizards.…”

“…Sections 5 μm thick were cut from the paraffin-embedded follicles in each phase of the follicular development (five lizards per phase) and processed for IHC as described by Cruz-Cano et al, 2023 [ 32 ]. They were deparaffinized in xylol and rehydrated in descending grades of ethanol.…”