Measurement of membrane permeability and the mitochondrial permeability transition

The mitochondrial permeability transition (PT) is an increase in the inner membrane permeability caused by the opening of a Ca2 +-activated high-conductance channel, the so-called PT pore (PTP) or mitochondrial megachannel (MMC). Recent data indicate that F-ATP synthase contributes substantially to the generation of the PTP, yet this hypothesis is the matter of controversy. In this chapter, we will describe an approach to study the pore, i.e., the evaluation of mitochondrial swelling by means of a decrease in the absorbance at 540 nm. This method should be useful to resolve apparent discrepancies in the literature and help solve emerging issues on the identity of mitochondrial pores.