Abstract: Abstract:Objective
To investigate the effect of urea transporter B(UT-B) gene on testosterone secreted by Leydig cells of male mice  by using UT-B gene knockout mouse models.Methods The UT-B gene knockout (UT-B－／－) mice were fed,bred and identified.5  UT-B wild type (UT-B+/+) male mice  and 5 UT-B－／－ male mice from the same genetic background aged  4 weeks were selected.The levels  of the serum testosterone and luteotropic hormone(LH) of two kinds of mice were detected by radioimmunoassay;the Leydig cells of two kinds of mice were isolated and cultured and then identified;the level of testosterone in culture supernatants was detected.Results The UT-B+/+ male mice and UT-B－／－ male mice were obtained  successfully;the primary Leydig cells were isolated and cultured and the cell purity was up to 80% identified by 3β-HSD staining method.The serum testosterone level  of    UT-B－／－  male mice aged 4 weeks ［（7.29±1.27）×10-2 μg•L^-1］was higher than that of UT-B+/+ male mice［（5.53±1.58）×10-2 μg•L^-1］（P<0.05），but there was no significant difference of serum LH levels  between two kinds of mice (P>0.05).The testosterone level  in the Leydig cells supernatants of  UT-B－／－ male mice［（17.300±1.179 ） nmol•L^-1］　was higher than that of UT-B+/+ male mice［(12.300±0.916 ) nmol•L^-1］（P<0.01）.
Conclusion The ability of Leydig cells secreting testosterone of UT-B－／－ male mice aged 4 week  is stronger than that of UT-B+/+ mice,which might be one of the reasons that the reproductive age of  UT-B－／－ male mice   is earlier than that of UT-B+/+ male mice.

Key words: urea transporter B, Leydig cells, testosterone, gene knockout