Antioxidant defence system in protein fractions of common carp (Cyprinus carpio) seminal plasma

Abstract

There are growing evidences that the damage which is caused to the spermatozoa by the reactive oxygen species (ROS) plays a key role in male infertility. The seminal plasma is endowed with many enzymatic and non-enzymatic antioxidants which protect the spermatozoa against oxidative stress. The present study was undertaken to compare the level of superoxide dismutase (SOD), glutathione reductase (GR) and glutathione peroxidase (GPx) in separated protein fractions of whole common carp Cyprinus carpio seminal plasma. Seminal plasma from six male common carp was separated into four fractions. The fractions differed from each other in their total seminal plasma protein content and antioxidant status. The highest value of SOD (2.81 ± 0.11 mU/mg protein) was found in fraction 4, and the lowest (1.83 ± 0.18 mU/mg protein) in fraction 1. There were significant variations (ANOVA; P = 0.05) in GR activity, mainly between fractions 1, 2, and 4. The lowest value of GPx activity (14.9 ± 0.4 mU/mg protein) was found in fraction 2; however, the GPx activity showed low variability among fractions. We conclude that distinct seminal plasma fractions differ in antioxidant capacity. The inclusion of fractions with high levels of SOD, GR, and GPx in sperm storage medium may enhance protection against oxidative stress and promote sperm survival during the in vitro storage.