Thiol Cathepsins and Oxidative Modification of Stallion’s Seminal Plasma Proteins with Normal and Low Percentage of Live Spermatozoa Post Cryopreservation

Background: Stallion sperms are very sensitive to cryopreservation. Free radicals generated during cryopreservation lead to spermatozoa membrane damage, decline in their viability and change the activity of cysteine cathepsins. On the other hand, cathepsins may involve in the utilization of oxidatively modified proteins. The present study was conducted to assess cysteine cathepsins activity and level of oxidatively modified proteins in seminal plasma of stallions with a low ( less than 30%) and normal ( greater than 30%) percentage of live spermatozoa post cryopreservation Methods: A total of 33 breeding stallions comprising 6 stallions of the Budennovskaya breed, 22 Arabian breed, 4 Soviet Heavy-Draft and 1 Bashkir breed. We assessed standard quality parameters in fresh and cryopreserved sperm, as well as cysteine cathepsins B,L,H activity, the level of oxidatively modified proteins in stallions seminal plasma with a low ( less than 30%) and normal ( greater than 30%) percentage of live spermatozoa post cryopreservation. Result: The group with a low percentage of live spermatozoa was characterized by decreased sperm quality, increased level of aldehyde dinitrophenylhydrazones (p=0.045) and ketone dinitrophenylhydrazones (p=0.049) of a neutral nature, as well as increased activity of cathepsin L (p=0.029). Evaluation of activity of cathepsin L and the concentration of oxidatively modified proteins in the seminal plasma can serve as a marker in the selection of stallions for sperm cryopreservation.