<p>We studied functional state of liver mitochondria in 5-6-week-old SHR rats. Parameters of respiration and oxidative phosphorylation were assessed. The obtained data were compared with the results of the Western blotting of protein subunits forming the mitochondrial respiratory chain complexes in the liver. The activity of antioxidant enzymes (SOD, catalase, and glutathione peroxidase) and the rate of H₂O₂ production were also examined in comparison with the control (WKY rats). An increase in the level of respiratory-chain complex V protein subunit, as well as a decrease in the activity of major mitochondrial antioxidant enzymes in SHR rat liver, was shown. The obtained results indicate the appearance of pathophysiological changes in the mitochondrial function in the liver (the organ that is not a primary target of the disease) of 5-6-week-old SHR rats (the age of first manifestations of arterial hypertension). These changes should be considered in future research into the pathogenesis of essential hypertension at its early stages.</p>