however, KGRE pretreatment attenuated busulfan-induced sperm number and motility reduction and decrease of serum testosterone (Figs. 4 and 5). In addition, we could not observe the dose- dependent effects of KGRE against busulfan-induced dysfunction of the male reproductive system. Further study is required to explain the lack of dose dependency of KGRE. Interestingly, busulfan did not induce complete sterility when we compared litter size with the control