One of the complications of diabetes mellitus (DM) is diabetic cardiomyopathy (DCM), the molecular mechanisms of pathogenesis of which have not been fully studied. Previously, the involvement of Na+/K+-ATPase and components of the Ca2+ transport system in cardiomyocytes in the development of DCM was shown. The aim of the work was to study the expression and activity of Na+/K+-ATPase and Ca2+-ATPase (SERCA2) in the myocardium of male Wistar rats in a model of streptozotocin (STZ)-induced prediabetes and overt type 1 diabetes (T1DM). STZ was administered at once i. p. in dose of 30–35 mg/kg. Rats with glucose levels above 11 mM were considered diabetic (STZ-D1 group), and those with moderate hyperglycemia were considered prediabetic (STZ-preD1 group). The activity of Na+/K+-ATPase and Ca2+-ATPase was determined (by the rate of release of inorganic phosphate, Pi), and the expression of the genes α1- and α2-isoforms of Na+/K+-ATPase, SERCA2 and Kir6.1, Kv7.1 and Kv2.1 potassium channels. In the control (C) group, the activity of Mg2+-dependent ATPase (α1- and α2-isoforms of Na+/K+-ATPase), sensitive to 1 mM ouabain, was 6.03±0.6 mmol Pi/g/h. In the STZ-D1 and STZ-preD1 groups, Na+/K+-ATPase activity did not differ from group C. The level of gene expression of α1- and α2- subunits of Na+/K+-ATPase in the STZ-D1 group decreased by more than 45%, then both in the STZ-preD1 group increased by 64 and 81%, which may indicate a high sensitivity of expression to insulinopenia. The activity of Ca2+-ATPase and the expression of the SERCA2 gene did not differ between the groups – probably, the 4-week period after STZ administration is not sufficient for the development of Ca2+-ATPase deficiency in the rat heart. The level of expression of the genes of the potassium channel subtypes Kv2.1, Kir6.1 and Kv7.1 increased in the STZ-preD1 group, which may indicate a certain contribution of the studied potassium channel subtypes to the adaptation mechanism to moderate hyperglycemia.
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