Transmembrane electric potential and physico-chemical states of thymocyte and liver mitochondria membranes in cold-acclimated rats

To evaluate the state of energetic processes in rats during various terms of cold exposure (+ 5 degrees C from 2 h to 49 days), the electric transmembrane potential of thymocytes (Delta Psi(t)) was used. This potential is a sum of the mitochondrial and plasmatic transmembrane potentials. It was show that the changes in Delta Psi(t) were similar to the changes in the transmembrane electric potential of liver mitochondria (Delta Psi(m)): the decrease past 2, 5 and 24 hours of cold exposure, the recovery on the 5th day and the great Fall on the 10th day. The latter was accompanied by the decrease in body temperature. Delta Psi(m) recovered to the 15-th day of exposure and exceeded the control level during the period of acclimation from 28 to 49 day resulting from the increase in the capacity of rat liver mitochondtia. From the 15-th day of cold exposure, Delta Psi(t) also increased, but its level did not amount to the control one even on the 49-th day. The characters of variations in lipid viscosity, protein-lipid interactions, and the contents of lipid peroxides and alpha-tocopherol were the same both in thymocytes and in liver mitochondria. The obtained data contradict the traditional considerations on the role of lipid peroxidation in the membrane funcion: high Delta Psi was accompanied by the increase in the content of alpha-tocopherol, but high level of lipid peroxides did not always induce the drop of this potential.