As it is well known, many antioxidants are used in order to increase of freezability of ram semen. While some antioxidants has prooxidant effect, some antioxidants give strong effect to sperm cells.
Could you please give your ideas on the criteria of antioxidant selection for using in semen freezing? Thanks
Data Effect of L-(+)-Ergothioneine (EGT) on Freezability of Ram Semen
During freezing the sperm undergo osmotic stress, cold stress and physical damage resulting in production of ROS. Also during freezing sperms are induced to partial capacitation state also termed as cryocapacitation which is not desirable. Desired antioxidative effect can be achieved by decreasing the production of ROS and nullifying its toxicity to the cell but at the same time capacitation effect should also be minimized. Hence antioxidants that do not change osmolarity to greater extent and and have anti capacitating effect is desirable.
I believe that most antioxidant studies are based on effects in other cell types and then empirically testing them at different concentration ranges. Antioxidants can behave very differently at different settings, and it is very difficult to say how they would behave in a different species or even with different extenders or freezing protocols. Most studies just find marginal benefits, if any.
We have some clue that supplementing antioxidant like Vit E is better than adding the same at freezing for improving freezing quality of semen in bull having semen freezability problems.
The purpose of the use of antioxidant is well explained by Vivek Singh. Any antioxidant that is water soluble works better than the one that is not, for example, Vit E. It is important that the agent mix properly in the extender, than float on, to do the job on ROS killing. This information is from unpublished research done for quality improvement in a commercial bovine semen production laboratory.
We have some studies (see my publication list, deer articles) showing that Trolox (soluble vit. E) works very well if added to thawed deer sperm, but it is detrimental if added before freezing. In ram results were mixed, depending if semen was refrigerated or thawed. GSH have yielded also mixed results both in ram and deer, but in pig (see Rodriguez-Gil, Yeste, etc.) it yielded very good results.
Thanks to all researchers for valuable answers...
An antioxidant must be stable , natural, assimilable by tissues and easily obtainable from a natural source...Also, it must chelate various divalent metallic cations , activate antioxidant enzymes , inhibit superoxid dismutase producting enzymes and not show aouto-oxidation physiological pH ...
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