[On the biotransformation of xenobiotics by rat liver mitochondria]

Rat liver mitochondria, isolated in succrose (0.25 mol/l), were frozen and stored for several weeks at -18 degrees C. Enzymic tests and electronmicroscopy were used to estimate freezing damage to mitochondria. The activities of the mitochondrial enzymes were altered significantly by freezing and thawing. The outer membrane enzyme activities were decreased by both, freezing and storing. On the contrary the activities of some inner membrane enzymes were initially increased by freezing (latency) and then decreased by storing. Storage of not frozen mitochondria suspensions lowered equally the activities of inner membrane enzymes and outer membrane enzymes. The decrease of the enzyme activities was connected to structural alterations, the mitochondrial membranes were damaged completely by freezing/thawing and storage.