Ovarian follicle development occurs within a physiologically hypoxic microenvironment, accompanied by the gradual accumulation of lactate derived from glycolysis. However, its role in the regulation of ovulation remains incompletely understood. In this study, 42 three-week-old female ICR mice were randomly divided into two groups of 21 each: the PMSG group and the PMSG + hCG group, to establish an hCG-induced superovulation mouse model. Samples were collected at 6h, 10h, and 14h after hCG injection, with seven samples per group at each time point. The result indicated the lactate concentration in ovarian granulosa cells (GCs) was significantly increased after hCG stimulation, peaking at 14h post-superovulation, suggesting a potential role for lactate during the ovulatory process. From these results, additional pharmacological interventions were performed in parallel to hCG treatment， such as Oxamate (inhibitor of lactate) group, Oxamate + Lactate group (lactate supplementation) and the C646 group (lactylation inhibition). To further understand how lactate metabolism regulates ovulation, we employed Western blot, qPCR, and ChIP-qPCR to examine its underlying molecular mechanism. We found that hCG-induced lactate accumulation selectively up-regulated histone H3 lysine 18 lactylation (H3K18la) in GCs. It was enriched on the promoter of Pgr, enhancing its transcriptional activation. Thus, enhancing PR protein expression and the transcriptional program of downstream ovulation-related genes. Pharmacological inhibition of lactate dehydrogenase or disruption of histone lactylation significantly decreased H3K18la modification and Pgr expression, inhibiting the efficacy of hCG-stimulated ovulation. In contrast, the addition of lactate from outside sources only partially rescued these effects. In order to confirm that the regulation is species-conserved, primary porcine granulosa cells were isolated and cultured in vitro, corresponding drug intervention confirmed that hCG promote PR protein lactylation, nuclear translocation, and transcriptional activation of downstream ovulation related genes via lactate accumulation. In conclusion, our results show here that hCG upregulates the H3K18la modification through inducing lactate accumulation which couples the hormonal signal with PR activation and its downstream gene expression to promote ovulation. Histone lactylation might be a new target of intervention in ameliorating human reproductive disorders or enhancing livestock.

To Cite This Article: Lu X, Wu G, Li H, Hua B, Zhou X, Deng J, Liu H and Shen M, 2026. H3K18 lactylation couples hCG-Induced lactate accumulation to progesterone receptor-dependent ovulation. Pak Vet J, 46(6): 1417-1428. http://dx.doi.org/10.29261/pakvetj/2026.136