Line and birth season effects on plasma testosterone and oxidative stress parameters in testis of maturing rabbits

Oxidative stress plays a key role in the male reproductive function. Differences between rabbit breeds have been found for testis size, seminiferous tubule diameter, number and size of interstitial and germ cells, etc. Traits related to the redox system could also be affected by genetic factors. It is likely that differences between breeds for these traits would lead to differences in reproductive maturation and fertility.We have investigated in the present paper the age-related changes of the plasma testosterone (TST) concentration, superoxide anion (O₂^?) radical formation, superoxide dismutase (SOD) activity, catalase (CAT) activity and thiobarbituric acid-reactive substances (TBARs) level in testis of rabbits in two breeds selected for different aptitudes (Caldes for growth rate and Prat for litter size). The effect of birth season for these traits was also assessed.Major changes in parameters related to oxidative stress were observed at an early age and most probably can be explained by the concomitant changes in testicular structure and function. Both lines showed similar developmental profiles and levels for all the variables studied. There was no interaction between line and birth season, consequently environmental conditions affected both lines in the same manner. Significant differences between males born in different seasons were found for O₂^? (4.84 ± 0.19 RLU/mg tissue min versus 5.67 ± 0.19 RLU/mg tissue min), SOD (6.12 ± 0.11 U/mg protein versus 7.09 ± 0.11 U/mg protein) and CAT (0.058 ± 0.002 K/mg protein versus 0.040 ± 0.002 K/mg protein). Future studies should take into account differences between seasons for a more precise analysis.