Optimized addition of nitric oxide compounds in semen extender improves post-thaw seminal attributes of Murrah buffaloes.

Semen dilution and cryopreservation alter the homogeneity of seminal plasma, resulting in a non-physiological redox milieu and consequently poor sperm functionality. Considering the concentration-specific bimodal action of nitric oxide (NO) in the regulation of sperm functions, cryopreservation media supplemented with optimized concentrations can improve the semen attributes. The present study aimed to evaluate the effect of adding an optimized concentration of sodium nitroprusside (SNP) and N-nitro-L-arginine methyl ester (L-NAME) in an extender on in vitro semen quality. An aliquot of semen samples (n = 32) from Murrah buffalo bulls (n = 8) was divided into control (C) and treatment (T-I: SNP in extender at 1 µmol/L; T-II: L-NAME in extender at 10 µmol/L). Fresh semen quality parameters showed no significant difference at 0 h except for the structural integrity in the T-II group. Post-thaw semen quality parameters and sperm kinematics using computer-aided sperm analysis (CASA) revealed significantly higher (p < 0.05) cryoresistance in the treatment groups. Viability, acrosome integrity, and membrane integrity were significantly higher (p < 0.05) in both treatment groups; however, the results were pervasive in T-II. Lower abnormal spermatozoa were observed in both T-I and T-II. SNP supplementation led to a significant rise (p < 0.05) in NO, whereas L-NAME reduced the NO concentration in post-thawed samples, which was directly correlated with different sperm functionality and associated biomarkers viz. total antioxidant capacity (TAC) and thiobarbituric acid reactive substance (TBARS). It was concluded that the cryopreservation media supplemented with SNP and L-NAME at 1 µmol/L and 10 µmol/L, respectively, lower the cryo-damage and improve post-thaw seminal attributes.

Bimodal interplay of reactive oxygen and nitrogen species in physiology and pathophysiology of bovine sperm function.

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are the mediators of redox activity and are known to perform concentration-specific bimodal roles. At lower concentrations, serves as a molecular messenger and signaling molecule while at higher concentrations induces stress which in turn alters the sperm's functional characteristics. Production of ROS and RNS cannot be prevented entirely and should not be followed as a pragmatic approach as they are involved in numerous sperm physiological functions. When the antioxidants defense armory is meager, excess generation of these species cross the physiological limits and inactivates essential metabolic enzymes and disrupts signal transduction altering normal sperm functions. As per the available literature, oxidants mostly arise as a result of pathological conditions or cryopreservation-induced injury. Dead and debilitated or abnormal spermatozoa and associated leukocytes release free radicals in an excess amount which elicits oxidative and nitrosative stressors that are potentially toxic to cryosurviving sperm. ROS plays a double edge sword effect on sperm function, as regulators of physiological mechanisms at low levels and as toxicants when produced at high concentrations. Recently nitric oxide (NO.) has emerged as a potential regulator of sperm physiology, in addition, found to mediate homeostasis of the seminal plasma microenvironment when semen samples are incubated with optimal concentrations of NO. compounds. The NO. compounds can provide some resistance to future stresses which are not usually harnessed by using the defensive strategy of supplementing antioxidants. Therefore, through the optimized addition of NO. donor and inhibitor in extender, the free radical-induced damage can be avoided without inhibiting their essential physiological effects on fertilization and subsequent embryo development. This article is intended to describe the role of reactive oxidants in the physiology and pathophysiology of spermatozoa and their relationship with various seminal attributes.