LAUSR

Study results on the condition of endogenous ethanol—acetaldehyde system in northern red-backed vole (Myodes (=Clethrionomys) rutilus Pallas, 1779), common species of northern latitudes, are presented. Concentrations of endogenous ethanol (EE) and acetaldehyde (EA) in blood, activities of alcohol dehydrogenase in ethanol oxidation reactions (ADHI) and liver acetaldehyde (ADHII) and aldehyde dehydrogenase (ALDH) reduction, and catalytic parameters of these enzymes are determined for winter and summer periods. Changes in ethanol—metabolizing dehydrogenase enzyme system in northern red-backed vole leading to statistically significant (p < 0.01) increase in blood EE and EA concentrations compared to white nonpedigreed laboratory rats without adaptations to cold (especially in winter period) are determined to serve ecoadaptive, antistress functions, comprising one of the systems for regulation of metabolism intensity in small mammals inhabiting extreme northern conditions. Ecological—physiological functions of EE and EA system are increasing the organism’s resistance to the influence of cold temperatures and maintaining thermoregulation even under rapid, considerable environmental temperature drops.