The temperature dependence of respiration and ATPase in rat liver mitochondria is altered by ethanol.

We studied hepatic mitochondria to determine the effects of ethanol in vitro and of chronic ethanol consumption on the temperature dependence (10 degrees-45 degrees C) of a) substrate oxidation, and b) ATP hydrolysis, with or without CCCP. Arrhenius plots showed the characteristic breaks around 20 degrees C both for electron transport and ATP hydrolysis with high energy of activation at low temperature and low energy of activation at high temperature. Ethanol, in vitro, generally lowered the energy of activation at high temperature and shifted the break in the Arrhenius plots to lower temperatures suggesting an increase in membrane fluidity. At 40 degrees C and above ethanol accelerated electron transport and greatly stimulated ATPase activity. In mitochondria from ethanol-fed rats, Arrhenius plots showed a shift in the breaks to a higher temperature, a finding which suggests a change in membrane structure, possibly associated with decreased fluidity. This may be an adaption of the mitochondrial membranes to counter the effect of ethanol on membrane structure.