Distributions of the surface charge density and surface potential over pore sizes for a meso-porous amine-containing silica gel have been calculated using different potential-to-charge relations. The surface charge density has been seen to fall down with decreasing the reduced pore size, chi R(p); herewith the effect of the electrostatic saturation becomes less marked and manifests itself up to chi R(p) similar to 3 as the Debye-Huckel equation is used, and up to chi R(p) similar to 1 as the Poisson-Boltzmann equation is used. The role of the spatial dispersion of the dielectric constant brought about by the electrostatic saturation in the charge regulation at porous solid/electrolytic solution interfaces has been analyzed on a quantitative level.