['To investigate the effect of lipid peroxidation on testosterone (T) in the serum and bcl-2 expression in the Leydig cells of aging male rats.', 'The D-galactose-induced subacute aging male rat model was established and 20 SD rats were randomly divided into two groups of equal number: a D-galactose (D) group and a control (C) group. The activity of superoxide dismutase(SOD) and the level of malondialdehyde (MDA) were examined by spectro-absorptiometer, the expression of bcl-2 by immunohistochemical method, and the concentration of serum T by radio-immunity technique.', '(1) The activity of SOD in the testis of the D group was (116 +/- 18.09) U/ mg x prot, significantly lower than in the C group [(156 +/- 31.02) U/mg x prot (P < 0.01)]. (2) The level of MDA in the testis of the D group was (1.77 +/- 0.41) nmol/mg x prot, significantly higher than in the C group [(1.19 +/- 0.15) nmol/mg x prot (P < 0.05)]. (3) Serum T in the D group was (2.39 +/- 0.90) nmol/L, significantly lower than in the C group [(8.95 +/- 2.53) nmol/L (P < 0.01)]. (4) The expressions of bcl-2 in the leydig cells of the D and C groups were (35.1 +/- 3.6)% and (49.6 +/- 7.4)% respectively, with statistical difference between them (P < 0.01).'] Does [ Lipid peroxidation affect serum T and Bcl-2 expression in the testis of aging male rats ]?