Seasonal changes in the level of endogenous ethanol and acetaldehyde in the blood of large herbivorous mammals of the Аrctic and Subarctic

We investigate seasonal changes in the state of endogenous system of ethanol/acetaldehyde metabolites in the organisms of the large herbivorous mammals of the Arctic and Subarctic – reindeer (R) and Yakut breed horse (YH). We focus on the content of endogenous ethanol (EE) and endogenous acetaldehyde (EA) in the blood of the animals, along with the activity and concentration of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) in their livers. We analyzed the involvement of the endogenous system in the adaptation mechanisms of the aboriginal herbivorous mammals to the extreme climate conditions at the high latitudes. The biomaterial (blood, liver) for the study was collected immediately after the slaughter in winter (December–January) and summer (June–July) in 2017– 2019. The animals led an active lifestyle throughout the year in native environment. The number of R in each season made 30, the number of YH – 40. The seasonal temperature fluctuations ranged from –50 °C (in winter) to +38 °C (in summer). We used the method of gas chromatography with mass spectrometry (GC-MS) to determine the EE and EA concentration in the animals’ whole blood. It has been shown that the levels of EE and EA in the blood of the large herbivorous mammals under study were significantly higher than those of the laboratory animals and humans. We detected seasonal dynamics in the content of metabolites, namely, a synchronous increase in their concentrations in the blood during the period of low ambient temperatures. The mechanism of the latter included seasonal changes either in isozyme forms of ADH and ALDH, which differed in their catalytic and physicochemical parameters in R, or in the concentration of enzymes in YH. These changes represent physiological and biochemical adaptive adjustments that increase resistance of the animals to the cold. An increase in the content of endogenous ethanol in the blood of YH and R prove that their reserve catabolic materials capable of generating biochemically useful energy under stressful conditions are included in the energy metabolism. Furthermore, an increase in the content of endogenous acetaldehyde represents a mechanism for reducing the overall level of bioenergetic processes with a redistribution of their intensity towards the increased generation of thermal energy. The physiological function of the system of endogenous ethanol, acetaldehyde and their metabolizing enzymes is to regulate (increase) the body’s resilience to the stressful impact of the cold.

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