Figure 7.

Schematic model of aquaporins (AQP) functioning under normal and oxidative stress conditions: (A) under normal condition, water enters through AQP7 and exits through AQP3. H₂O₂ produced in low amount exits from mitochondria through AQP8; and (B) under oxidative stress condition, H₂O₂ reduces water inflow and outflow through AQP7 and AQP3, thus affecting sperm motility. H₂O₂ reduces also AQP8 permeability that hampers H₂O₂ wasting; this leads to H₂O₂ accumulation into mitochondria, reduced AQP production and thus to reduced sperm motility. Intracellular AQP11 could be involved in the end stage of cytoplasm removing.