TPP+ inhibits Na+-stimulated Ca2+ efflux from brain mitochondria

Abstract Tetraphenylphosphonium (TPP + ) inhibits Na + -stimulated Ca 2+ efflux from brain mitochondria. Half inhibition is observed when 1·10 −8 M TPP + is present in the medium. Some other lipophylic cations show similar effect. TPP + must be used carefully for measuring transmembrane potential because of its effects on the system studied. TPP + will be a useful tool to study Ca-transport system in mitochondria.