[Effect of excess cooling on rat liver mitochondria: release of K+ and malate dehydrogenase at lipid phase transition temperatures].
The effects of cooling within the temperature range of 0-25 degrees on the state of mitochondrial membranes was studied. The increase in membrane permeability for K+ and malate dehydrogenase which is localized in mitochondrial matrix, served as an index of membrane structural damage within the given temperature interval. In order to prevent crystallization of the aqueous phase upon cooling ethylene glycol was added to the medium to reach a final concentration of 40%. The decrease of temperature resulted both in the release of K+ and in the increase of the activity of free malate dehydrogenase. A drastic increase in the mitochondrial membrane permeability to K+ and malate dehydrogenase was observed within the temperature range of -6 -- -14 degrees, showing a maximum at -10 degrees. At -14 degrees the rate of K+ and malate dehydrogenase release was lower; however, further cooling (down to -20 degrees) induced another increase of permeability. The disruption of mitochondrial at negative temperatures after addition of 1.25 M NaCl to the incubation mixture caused a temperature-dependent release of the proteins into the supernatant. After ultracentrifugation of the membrane fragments at 140 000 g for 60 min the soluble proteins were detected in the samples coled down to -10 degrees. It was concluded that the changes in the state of mitochondrial membranes are due to the phase transitions of the inner membrane lipids.
D000818:Animals; D003080:Cold Temperature; D007425:Intracellular Membranes / Q000378:metabolism*; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000378:metabolism*; D008563:Membrane Lipids / Q000502:physiology*; D008930:Mitochondria, Liver / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D051381:Rats
D008563:Membrane Lipids; D008291:Malate Dehydrogenase; D011188:Potassium
Vliianie pereokhlazhdeniia na mitokhondrii pecheni krysy: osvobozhdenie kaliia i malatdegidrogenazy pri temperaturakh fazovykh perekhodov lipidov.