A spectrophotometric study of the spontaneous and microsome-induced swelling of rat-liver mitochondria.

The effect of microsomes on the swelling of rat liver mitochondria has been studied. A kinetic study of the changes in the optical density of the mitochondrial suspension during swelling revealed that the swelling is preceded by a lag. Addition of microsomes shortens this lag period, but otherwise the microsome-induced swelling resembles closely spontaneous swelling. The duration of the lag depends on the concentration of mitochondria, pH, temperature and osmotic pressure. The active component of the microsomes has the properties of a fatty acid. Indeed, fatty acids have been shown to produce the same effect. Some aspects of the spontaneous and the microsome-induced swelling are discussed.