The electroneutral transport of anions into mitochondria causes apparent saturation characteristics.

A theoretical analysis of the apparent saturation characteristics of anion accumulation by mitochondria is presented. The decrease in the accumulation ratio observed with increasing extramitochondrial anion concentration can be caused solely by the cotransport of protons due to the electroneutral transport mechanism and might not indicate that mitochondria have a limited anionic capacity. On this basis a mathematical model of anion distribution was developed which sufficiently describes the published experimental data of anion accumulation by mitochondria.