OBJECTIVETo preliminarily study the effect of prepubertal exposure of male SD (Sprague-Dawley) rats to diethylstilbestrol (DES) on the apoptosis of spermatogenic cells after sexual maturation and its mechanism.

METHODSThirty 21-day-old male SD rats were randomly divided into 4 experimental groups, DES 0.01, 0.1, 1.0 and 10.0 microg/(kg x d) and 1 control group. The experimental groups were injected (s.c.) with different doses of DES (dissolved in corn oil) during prepuberty [from postnatal day (PND) 22 to PND 35] and the control group with medium only. The apoptosis and related proteins Bcl-2 and Bax expressions of testicular spermatogenic cells were studied with TUNEL and immunohistochemistry after the rats sexual maturation (at PND 64).

RESULTSCompared with the control group, the apoptosis of testicular spermatogenic cells in the DES 0.01 microg/kg group had no difference, but significantly increased in the DES 0.1, 1.0 and 10.0 microg/kg groups and the apoptosis increased with the increase of DES dose. In the control and DES 0.01 microg/kg groups, Bax protein expressed weakly but Bcl-2 protein strongly in spermatogenic cells. With the increase of DES exposure, Bax protein expression in spermatogenic cells increased but Bcl-2 protein expression decreased.

CONCLUSIONPrepubertal exposure of SD rats to inappropriate dose of DES can make the apoptosis of spermatogenic cells increase after sexual maturation. Bax and Bcl-2 proteins participate in the apoptotic course caused by prepubertal DES exposure.