Determinación del efecto post congelación de microdosis de menaquinona-4 en semen ovino

Abstract

The ovine semen presents particularly high levels of polyunsaturated fatty acids (PUFAs) in its plasma membrane. This composition causes high instability, making sperm cells prone to reactive oxygen species (ROS) formation. Oxidative stress (OS), triggered by thermal shock and atmospheric oxygen during cryopreservation, increases susceptibility to lipid peroxidation (LPO). Antioxidant supplementation acts and reacts as a protective strategy against this damage. This study proposed Menaquinone-4 (MK-4), a vitamin K homolog from the Menaquinone group, as a potential sperm antioxidant. We tested in the Reproduction Laboratory at Universidad Católica de Cuenca three microdoses of MK-4 (0.5 µM, 1 µM, 2 µM) to assess its effect on post-thaw ovine semen. Results showed dose-dependent variability compared to the control. At 2 µM, membrane integrity parameters were similar to the control. However, the 0.5 µM dose improved progressive motility. These differences suggest that MK-4 efficacy depends on the enzymatic capacity of sperm cells. The absence of UBIAD1 enzyme in donor gonads, due to the lack of endoplasmic reticulum and Golgi apparatus in sperm cells, limits MK-4 utilization. Therefore, antioxidant performance depends on intracellular enzyme availability. This biochemical limitation explains the inconsistent results across doses. MK-4 may offer cryoprotective benefits under specific cellular conditions, particularly in sperm with active metabolic machinery. Findings highlight the importance of considering enzymatic context when using fat-soluble antioxidants in cryopreservation protocols. Further research is needed to optimize MK-4 concentrations and evaluate its in vivo impact on fertility parameters. Keywords: PUFA; EO; LPO; ROS; UBIAD1