Uptake of magnesium and calcium by mitochondria in exchange for hydrogen ions

1. 1. Rat-liver mitochondria take up Mg²⁺ in exchange for H⁺. 2. 2. Inorganic orthophosphate is not essential for Mg²⁺ uptake. 3. 3. Inorganic orthophosphate uptake can take place in the absence of Mg²⁺. 4. 4. Rat-liver mitochondria take up Ca²⁺, in part at least, by the same route as Mg²⁺. H⁺ is exchanged for Ca²⁺. 5. 5. The divalent cations appear to share a common transport mechanism with K⁺. 6. 6. It is concluded that mitochondrial cation-transport mechanism is a system which extrudes H⁺. Any one of several cations may be taken up in exchange. 7. 7. An explanation is advanced for the opposing effects of 2,4-dinitrophenol and Ca²⁺ on mitochondrial swelling. 8. 8. The sensitivity and specificity of atomic absorption spectrophometry facilitated analysis of Ca²⁺ and Mg²⁺.