Physiological Functions and Metabolism of Endogenous Ethanol and Acetaldehyde in the Reindeer

Abstract

This study addresses for the first time the seasonal (winter–summer) dynamics of endogenous ethanol (EE) and acetaldehyde (EA) blood levels as well as of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) activities and catalytic properties in the liver of the reindeer. EE blood level was 1.89 ± 0.11 mM in summer and 1.41 ± 0.10 mM (i.e. 1.34 times lower) in winter (p< 0.05). Seasonal dynamics of EA blood levels was opposite: 3.06 ± 0.28 μM in summer and 12.62 ± 0.76 μM (i.e. 4.12 times higher) in winter (p< 0.05). In winter, there was a decrease in activities of ADH_II in the acetaldehyde reduction reaction (4.0 times) and ALDH (3.3 times) in the liver (p< 0.05). This led to an increased winter blood level of EA in cold-adapted animals. Our results suggest that EE and EA, as interrelated metabolites, make up one of the systems that regulate the metabolic rate and eventually reduce the intensity of energy metabolism in the reindeer. This consi derably extends the possibilities for northern species to exist under extreme environmental conditions of cold regions. Apparently, a major ph ysiological function of the system that includes EE, EA and relevant enzymes is to increase cold tolerance of an organism due to the inhibitory effect of EA on mitochondrial terminal oxidation which reduces the intensity of aerobic processes.