This study was planned to investigate the protective effects of melatonin against heat stress on the reproductive health, focusing on ovarian function and luteal regression. Specifically, it examined the pathways of necroptosis during luteal regression induced by prostaglandin F_2α (PGF) in heat-exposed rats. Seventy-five immature female Sprague-Dawley rats were hormonally primed intra-peritoneally with Pregnant Mare's Serum Gonadotropin (PMSG) and human Chorionic Gonadotropin (hCG). After 24h, the rats were divided into three groups (n=25 per group): Non-Heat Exposure (NHE); rats were housed under standard conditions. Heat Exposure (HE); rats were exposed to 41°C for 2h daily for 7 days. Melatonin+Heat Exposure (M+HE); rats were exposed to the same heat conditions as the HE group, with melatonin was administered intra-peritoneally at 10mg/kg body weight. On Day 7, all rats were injected intra-peritoneally with PGF, and euthanized at 0, 2, 8, 16, or 24h post-PGF injection (n=5 on each time point). Blood samples were collected for serum progesterone analysis, and ovaries were harvested for Transmission Electron Microscopy, immunohistochemistry and Western blot analysis. The results revealed that heat stress caused significant down-regulation of steroidogenic proteins (HSD3B and CYP11A1) and elevated necroptotic markers (RIPK1 at 16h, RIPK3 and p-RIPK3 at 24h) post-PGF treatment. Heat exposure also reduced superoxide dismutase (SOD) and catalase (CAT) activities and elevated malondialdehyde (MDA) levels. Conversely, melatonin treatment restored steroidogenic protein expression (StAR and CYP11A1), increased SOD and CAT activities, decreased MDA levels, and reduced necroptosis markers (particularly RIPK3 and p-RIPK3 levels at 16 and 24h). These findings demonstrate the cytoprotective role of melatonin in countering heat-affected luteal regression through modulation of RIPK1/RIPK3 signaling, antioxidant defense enhancement, and preservation of steroidogenesis.

To Cite This Article: Tavakolikazerooni H, Tariq M, Yu H, Ullah S, Ennab W, and Mao D, 2025. Melatonin Modulates Necroptosis and Enhances Antioxidant Defense during PGF-Induced Luteal Regression in Heat-Exposed Rats. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.008