Induced sub-lethal oxidative damage affects osmotic tolerance and cryosurvival of spermatozoa
Franziska Ertmer A , Harriëtte Oldenhof A E , Saskia Schütze A B , Karl Rohn C , Willem F. Wolkers D and Harald Sieme A
+ Author Affiliations
- Author Affiliations
A Clinic for Horses – Unit for Reproductive Medicine, University of Veterinary Medicine Hannover, Bünteweg 15, D-30559 Hannover, Germany.
B National Stud Lower Saxony, Spörckenstraße 10, D-29221 Celle, Germany.
C Institute of Biometry, Epidemiology and Information Processing, University of Veterinary Medicine Hannover, Bünteweg 2, D-30559 Hannover, Germany.
D Institute of Multiphase Processes, Leibniz Universität Hannover, Callinstrasse 36, D-30167 Hannover, Germany.
E Corresponding author. Email: harriette.oldenhof@tiho-hannover.de
Reproduction, Fertility and Development 29(9) 1739-1750 https://doi.org/10.1071/RD16183
Submitted: 3 May 2016 Accepted: 2 September 2016 Published: 19 October 2016
Abstract
If the physiological balance between production and scavenging of reactive oxygen species (ROS) is shifted towards production of ROS this may result in accumulation of cell damage over time. In this study stallion spermatozoa were incubated with xanthine and xanthine oxidase (X–XO) to artificially generate defined levels of superoxide and hydrogen peroxide resulting in sub-lethal oxidative damage. The effects of X–XO treatment on various sperm characteristics were studied. Special emphasis was placed on sperm osmotic tolerance pre-freeze and its correlation with cryosurvival, given that cryopreservation exposes cells to osmotic stress. ROS accumulation occurred predominantly in the sperm midpiece region, where the mitochondria are located. Exposing spermatozoa to increasing X–XO concentrations resulted in a dose-dependent decrease in sperm motility. Percentages of plasma membrane-intact spermatozoa were not affected, whereas stability of membranes towards hypotonic stress decreased with increasing levels of induced oxidative stress. Infrared spectroscopic studies showed that X–XO treatment does not alter sperm membrane phase behaviour. Spermatozoa exposed to higher oxidative stress levels pre-freeze exhibited reduced cryosurvival. Centrifugation processing and addition of catalase were found to have little beneficial effect. Taken together, these results show that treatment of spermatozoa with X–XO resulted in different levels of intracellular ROS, which decreased sperm osmotic tolerance and cryosurvival.
Additional keywords: antioxidants, centrifugation processing, cryopreservation, equine spermatozoa, membrane phase behaviour, reactive oxygen species.
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