In summary, the results from the present study suggest that long-term treatment with haptoglobin improved erectile function due to up-regulation of eNOS-PDE5 expression and down-regulation of the isoform of NADPH oxidase (gp91phox) and oxidative/nitrosative stress in the penises of SCD mice. The gene discussed is PDE5A; the disease is Schnyder corneal dystrophy.