Effects Of Low Androgen Status On SO₂ Signaling Pathway In Corpus Cavernosum Of Rats

Objective:This study aimed to investigate the relationship between SO₂ signaling pathway and the changes in erectile function under low androgen levels.Methods:Thirty-six healthy male SD rats were randomly divided into six groups?6 rats/group?after adaptive feeding for one week,including group A?4-week androgen replacement group?,group B?4-week castration group?,group C?4-week sham group?,group D?8-week androgen replacement group?,group E?8-week castration group?and group F?8-week sham group?.Rats in the groups A and D were subcutaneously injected with testosterone propionate at 3 mg/kg qod after castration.The maximum intracavernous pressure/mean arterial pressure(ICP_max/MAP)and the relative content of SO₂ in the penile corpus cavernosum were measured.Protein expressions of aspartate aminotransferase?AAT1 and AAT2?,cysteine oxidase?CDO?,phosphorylation of endothelial nitric oxide synthase?P-eNOS?and endothelial nitric oxide synthase?eNOS?were detected by Western Blot.Expressions of AAT1,AAT2 and CDO in the penile corpus cavernosum were detected by immunohistochemistry.The mRNA expressions of AAT1,AAT2and CDO in the penile corpus cavernosum were detected by RT-qPCR.Results:After stimulation of the major pelvic ganglion with 3 V and 5 V,ICP_max/MAP in the castration groups?group B:0.39±0.04,0.55±0.01;group E 0.24±0.02,0.39±0.02?decreased significantly as compared to the replacement groups?group A:0.66±0.04,0.81±0.02;group D 0.64±0.04,0.79±0.01?and sham groups?group C:0.65±0.04,0.81±0.01;group E:0.64±0.04,0.79±0.04??p<0.01?,the 8-week castration group?E?was significantly decreased as compared to the 4-week castration group?B??p<0.01?,and there was no significant difference among groups A,C,D and F.The expressions of AAT1,AAT2 and CDO in rat penile corpus cavernosum by Immunohistochemistry show that AAT1,AAT2 and CDO are mainly expressed in the cytoplasm of vascular endothelial cells,with very little expression in the smooth muscle cell cytoplasm.The levels of expression of AAT1,AAT2 and CDO were quantified by measurement of integrated optical density which show that the castration groups?group B:1029.09±240.35,1081.77±33.47,871.56±239.25;group E:399.39±289.97,492.12±38.20,434.75±119.17?decreased significantly as compared to the replacement groups?group A:1634.49±285.78,1655.98±158.14,1525.79±24.00;group D:1685.44±205.22,1622.55±124.05,1560.98±24.88?and sham groups?group C:1627.94±111.82,1642.97±187.00,1568.72±84.55;group F:1621.20±79.05,1601.54±124.15,1593.34±74.44??p<0.05?.Expressions in the 8-week castration group?E?decreased significantly as compared to the 4-week castration group?B??p<0.05?.Furthermore,there was no remarkable difference between the replacement groups?A and D?and the sham groups?C and F?.As compared to the replacement groups?group A:1.20±0.05,1.23±0.06,1.17±0.07;group D:1.18±0.07,1.18±0.06,1.23±0.03?and sham groups?group C:1.19±0.06,1.19±0.06,1.19±0.03and group F?,protein expressions of AAT1,AAT2,CDO in the castration groups?group B:0.87±0.04,0.81±0.10,0.80±0.05;group E:0.46±0.05,0.45±0.12,0.47±0.10?decreased significantly?p<0.01?,while there was no significant difference between the castration groups?A and D?and sham groups?C and F?.Moreover,protein expressions in the 8-week castration group?E?decreased significantly as compared to the 4-week castration group?B??p<0.01?.As compared to the replacement groups?A and D??1.09±0.04,1.05±0.09?and sham groups?C and F??1.02±0.07,1.04±0.06?,P-eNOS/eNOS decreased significantly in the castration groups?B and E??0.57±0.04,0.36±0.04??p<0.05?.P-eNOS/eNOS in the 8-week castration group?E?decreased significantly as compared to the 4-week castration group?B?,while there was no significant difference between the replacement groups?A and D?and sham groups?C and F?.As compared to the replacement groups?group A:1.17±0.03,1.26±0.13,1.23±0.05;group D:1.13±0.05,1.16±0.09,1.18±0.14?and sham groups?group C:1.13±0.03,1.19±0.04,1.18±0.04;group F:1.13±0.02,1.25±0.10,1.29±0.09?,the mRNA expressions of AAT1,AAT2 and CDO in the castration groups?group B:0.86±0.01,0.88±0.08,0.72±0.16;group E:0.38±0.04,0.36±0.09,0.41±0.14?decreased significantly?p<0.05?.The relative mRNA expressions in the 8-week castration group?E?decreased significantly as compared to the 4-week castration group?p<0.05?,while there was no significant difference between the replacement groups?A and D?and sham groups?C and F?.As compared to the replacement groups?A and D??50.32±2.00,51.55±0.71?and sham groups?C and F??52.05±0.99,52.52±3.18?,SO₂ contents in the castration groups?B and E??45.44±1.24,40.70±3.72?decreased significantly?p<0.05?.SO₂ content in the8-week castration group?E?decreased significantly as compared to the 4-week castration group?B?,while there was no significant difference between the replacement groups?A and D?and sham groups?C and F?.Conclusion:Low androgen levels can inhibit the SO₂ signaling pathway by inhibiting the expressions of AAT1,AAT2 and CDO,thus reducing NO production by down-regulating e NOS,which finally inhibits the relaxation function of rat penile corpus cavernosum.