Is Zn²⁺ transported by the mitochondrial calcium uniporter?

Zinc ions were found to inhibit Ca²⁺ uptake by rat liver mitochondria driven by succinate respiration but not that by a valinomycin‐induced membrane potential. Zn²⁺ at 1 μM or higher concentrations induced a lowering of the membrane potential under the former but not the latter conditions. It is concluded that it is the lowered membrane potential in the presence of Zn²⁺ that reduces the rate of respiration‐driven Ca²⁺. Ruthenium red was found to inhibit the uptake of Zn²⁺ but had no influence on its action upon the membrane potential. Zn²⁺ did not affect the Ruthenium red‐insensitive Ca²⁺ efflux. Ca²⁺ stimulated the uptake of Zn²⁺. It is concluded that Zn²⁺ may be transported by the mitochondrial calcium uniporter but that it may have access to sites required for inhibition of respiration by other routes.