Quantitative real-time RT-PCR analyses of the androgen dependence of Spag11a in the epididymis. Mice were castrated, and the epididymides were isolated for RNA extraction after 6 h, 1 d, 3 d, 5 d, and also 3 d, 5 d castration with testosterone replacement therapy (3d + T, 5d + T). The expression levels were normalized to beta-actin. The error bars represent the standard error of the mean (SEM, n = 3). The results demonstrated that Spag11a was modestly up-regulated at 6 hours to 1 day following castration before being significantly down-regulated (P < 0.001) 3–5 days after castration. The expression levels after testosterone (T) injection (0.5 mg/mouse/day) for 3d + T and 5d + T were similar to control non castrated (Co). The difference between the expression levels at 3–5 d and 3d + T was significant (P < 0.001), confirming the effectiveness of the T replacement therapy.