​Localization of Orexin and its Receptor in Corpus Luteum and in vitro Effect of Orexin on Progesterone Production from Luteal Cells in Buffalo

Abstract

Background: Orexin is a hypothalamic neuropeptide involved in regulating various biological functions, including reproduction. The study aimed to investigate the immunolocalization of orexin and its receptors in the corpus luteum in buffalo (Bubalus bubalis) ovary and the effect of orexin on progesterone production. Methods: The study was carried out on buffalo ovaries, each with a different developmental stage of corpus luteum (CL) (n=10 for each stage). The CLs were separated out from ovaries for immunolocalization of orexin and its receptors in CL. In the in vitro study, luteal cells were cultured and treated with recombinant orexin at 0.1, 1 and 10 ng/mL doses for 48h and P4 concentration in the spent media was determined by ELISA. Result: Results of the present study revealed that orexin and its receptors are localized in the cytoplasm of large and small luteal cells of CL. The immunoreactivity varied with a stage-specific difference in CL. The present study also revealed that orexin inhibits P4 production in cultured luteal cells. The findings indicate orexin affects luteal dynamics and reproductive functions in buffalo (Bubalus bubalis).

Orexin system in buffalo ovarian follicles and effect of orexin on oestradiol production

“…In our previous studies, we have demonstrated the expression of the PPO and orexin receptors (OX1R and OX2R) in the corpus luteum of the buffalo ovary (Sardar et al, 2020). We also observed the physiological role of OXA on progesterone production from luteal cells (Sardar et al, 2023).…”

“…All these shreds of evidence specifically suggest the local presence of the orexigenic system on ovarian follicles. Not only in the follicles, but the presence of orexins and their receptors have also been reported in corpus luteum in the ovary of rats (Cataldi et al, 2012), pigs (Basini et al, 2018;Nitkiewicz et al, 2014) and buffalo (Sardar et al, 2020(Sardar et al, , 2023. Apart from the ovary, the presence of the orexigenic system has been documented in other female and male reproductive tissues, including the placenta and uterus (Smolinska et al, 2015) and testes (Barreiro et al, 2005).…”

“…In the bovine ovary, there is no evidence regarding the orexin system, which consists of PPO, OXA, OXB, OX1R, and OX2R. In the buffalo ovary, our previous study showed the presence of orexins and their receptors in the corpus luteum and the role of orexin on progesterone production (Sardar et al, 2020, 2023). Yet, no report is available concerning orexin in the ovarian follicles of water buffalo ( Bubalus bubalis ).…”