Published online by Cambridge University Press: 05 April 2021
Oxidative stress (OS) is the consequence of an imbalance between reactive oxygen species (ROS) and the failure of antioxidants to neutralize excessive ROS production. Although many sperm functions require physiological levels of ROS, excessive levels of ROS are detrimental to the sperm . OS is one of the most common etiologies of male infertility affecting 30–80 percent of infertile men [2, 3]. The role of OS in men with unexplained infertility has been clearly established . OS affects sperm quality as a result of alterations in proteins, lipid peroxidation, DNA damage and apoptosis . Damage to sperm DNA can compromise the contribution of paternal genome to the embryo . Hence the advent of numerous tests to diagnose OS in the semen. There are several laboratory tests available to measure OS – both direct and indirect. Direct tests measure OS or free radicals such as ROS and reactive nitrogen species. These include chemiluminescence, nitroblue tetrazolium, cytochrome C reduction test, electron spin resonance, fluorescein isothiocynate (DFITC)-labeled lectins, and measurement of oxidation reduction potential. Indirect tests measure oxidized products resulting from ROS sources such as the oxidized form of nicotinamide adenine dinucleotide (NADPH)-oxidase in the sperm, the reduced form of NAD (NADH)-dependent oxidoreductase in mitochondria, or leukocytospermia. These include myeloperoxidase or Endtz test, antioxidants (both enzymatic and non-enzymatic), lipid peroxidation, and DNA damage. In this chapter we will discuss the indirect tests that are available to assess OS and also elaborate on the interpretation and their clinical significance [4, 5].