In the Corynorhinus mexicanus four enzymes related to 
Reactive Oxygen Species (ROS) modulation are present in 
the cephalic and caudal region of the epididymides during 
the progress of the epididymis sperms and their maturation, 
but interesting to say the activity of the Super Oxide 
Dismutase (SOD) is not present or perhaps it is inhibited in 
both epididymal segments in the post testicular phase of the 
sperm storage function. The SOD is present during the 
period of maturation and during the transport of the sperms, 
but it is almost totally inhibited or not present in both 
epididymal segments during the storage, as well as an 
absence in the sperm cells SOD activity. It is interesting to 
observe that the Gamma Glutamyl Transpeptidase (GGT) 
and Glutathione PeroXidase (GPX) presents a complete 
pattern contrary to that of the SOD; its activity is low during 
the period of production and maturation of the epididymal 
sperms, but present an important activity in both segments 
of the epididymis during the storage phase. The activity of 
CATalase (CAT) is preserved relatively high during the 
whole reproductive cycle indicating its importance in the 
protection of the spermatic cells against the effect of 
Hydrogen peroxide (H2O2). However it is important to 
mention that its activity is significantly higher in the tail of 
the epididymis during the maturation and particularly 
during the storage process. In sperm from the cephalic and caudal region, the CAT activity reaches its highest levels at 
the beginning of September and the lowest at the end of the 
same month. In the epididiymal fluid the CAT activity 
shows a similar pattern in the cephalic region from that 
found for SOD and GGT/GPX in both regions. The redox 
balance associated with the microenvironment, through 
which the sperms pass, must be specific and differentially 
controlled to assure its adequate function