Effect of low androgen levels on IKca and SKca3 channels in rat penile corpus cavernosum.

We investigated whether low androgen levels affected erectile function by regulating the expressions of intermediate-conductance Ca2+ -activated K+ channel (IKca) and small-conductance Ca2+ -activated K+ channel 3 (SKca3) in corpus cavernous of rats. Thirty-six healthy male SD rats were randomly divided into the 4-week control group, 4-week castration group, 4-week androgen replacement after castration group, 8-week control group, 8-week castration group and 8-week androgen replacement after castration group, respectively. The rats in the androgen replacement groups were subcutaneously injected with testosterone (3 mg/kg) every other day after castration. After 4 and 8 weeks, maximum intracavernous pressure/mean arterial pressure (ICPmax /MAP) was measured. Expressions of IKca, SKca3, endothelial nitric oxide synthase (eNOS) and P-eNOS in penile corpus cavernosum were detected. ICPmax /MAP decreased significantly in the castration groups as compared to the control groups and the androgen replacement groups (p < 0.01). mRNA expressions of IKca and SKca3 decreased significantly in the castration groups as compared to the control groups and androgen replacement groups (p < 0.01). Protein expressions of eNOS, P-eNOS, IKca and SKca3 in the castration groups were significantly reduced as compared to the control groups and androgen replacement groups (p < 0.01). Under low androgen levels, ICPmax /MAP can be reduced by down-regulating the expressions of SKca3 and IKca, inhibiting P-eNOS/eNOS and reducing eNOS bioactivity.