OBJECTIVETo analyze the expression of inducible nitric oxide synthase (iNOS) in the testis tissues of Fmr1 (fragile X mental retardation 1) knockout and wild-type male mice in different developmental stages, and provide background information for researches on fragile X syndrome.

METHODSThis study included 4, 6, 8 and 10 weeks old Fmr1 knockout and wild-type male mice, 6 in each age group. We identified the genotype of the mice by PCR, and detected and compared the expression of iNOS in the testis tissues of the Fmr1 knockout and wild-type mice by immunohistochemistry.

RESULTSThe iNOS expression was weakly positive in the Leydig cells of the 4-week-old mice, moderately positive in the 6-week-old ones, and strongly positive in 8- and 10-week-old ones, significantly weaker in the Fmr1 knockout than in the wild-type ones.

CONCLUSIONThe expression of iNOS significantly decreases in the testis of Fmr1 knockout mice, suggesting that iNOS may be involved in the pathogenesis of fragile X syndrome.