Background Serum testosterone levels have been found lower in acute ischemic stroke male patients.However,the exact mechanism remains unclear.In the present study,we measured serum testosterone levels,steroidogenesisrelated genes and Leydig cells number in experimental transient cerebral ischemia male rats to elucidate the mechanism.Methods The middle cerebral arteries of adult male Sprague-Dawley rats were sutured for 120 minutes and then sacrificed after 24 hours.Blood was collected for measurement of serum testosterone,follicular stimulating hormone and estradiol levels,and testes were collected for measurement of steroidogenesis-retated gene mRNA levels and number of Leydig cells.Results Serum testosterone levels in rats after cerebral ischemia were significantly lower (0.53±0.16) ng/ml,n=7,mean±SE) compared with control ((2.33±0.60) ng/ml,n=7),while serum estradiol and follicular stimulating hormone levels did not change.The mRNA levels for luteinizing hormone receptor (Lhcgr),scavenger receptor class B member 1 (Scarb1),steroidogenic acute regulatory protein (StAR),cholesterol side chain cleavage enzyme (Cyp11a1),3β-hydroxysteroid dehydrogenase 1 (HSD311),17α-hydroxylese/20-lyase (Cyp17a1) and membrane receptor c-kit (kit) were significantly downregulated by cerebral ischemia,while luteinizing hormone,Kit ligand (KitL),17β-hydrosteroid dehydrogenase 3 (HSD17β3) and 5α-reductase (Srd5a1) were not affected.We also observed that,relative to control,the Leydig cell number did not change.Conclusions These results indicate that transient cerebral ischemia in the brain results in lower expression levels of steroidogenesis-related genes and thus lower serum testosterone level.Transient cerebral ischemia did not lower the number of Leydig cells.