Objective     To investigate the degrees of acute impairment of the Leydig cell structure and testosterone synthesis caused by different doses of 

60

Co-γ in rats.      Methods     Sixty male SD rats were equally randomized into five groups (n=12): a normal control group (group A)

and four bilateral testicular

60

Co-γ radiation groups

i.e.

a 4 Gy + 4 Gy group (group B)

a 6 Gy + 6 Gy group (group C)

a 2 G

y + 10 Gy group (group D)

and a 6 Gy + 8 Gy group (group E). The radiation time interval was 24 h. The serum luteinizing hormone (LH) and testosterone (T) levels were measured by ELISA

the structural changes of Leydig cells were observed by light microscope

and the mRNA expression levels of steroidogenic acute regulatory protein (StAR) and cytochrome P450 side chain cleavage enzyme (P450scc) from Leydig cells were measured by RT-PCR 48 h after the radiation.      Results     Compared with group A

the serum LH levels in groups B

C

D and E were significantly higher (P0.05)

and the serum T levels were significantly lower (P0.05). Under the optical microscope

the Leydig cells in groups B

C

D and E exhibited size decrease

quantity decrease

cytoplasm decrease

nuclear shrinkage

and chromatin condensation and anachromasis. The mRNA expression levels of StAR and P450scc in groups B

C

D and E were lower than those in group A (P0.05).      Conclusion    

60

Co-γ causes obvious impairment of Leydig cell structure and testosterone synthesis in rats. The impairment degree is positively correlated with not only the total dose but also the maximum single dose.