A Decrease in the Content of Giant Obscurin Isoform during the Development of Isoprenaline-Induced Myocardial Injury in Rats.

We studied changes in the content of obscurin and the corresponding mRNA in the left ventricle of rat heart during the development of isoprenaline-induced myocardial injury. Myocardial injury was induced by subcutaneous injection of β-adrenoreceptor agonist isoprenaline hydrochloride at a dose of 150 mg/kg of body weight twice with a 24-h interval. On day 14, the animals were euthanized. An increase (by 28.7%; p ≤ 0.01) in heart weight, as well as an increase (by 17.7%; p ≤ 0.01) in the heart-to-body weight ratio in rats after isoprenaline injection were observed, indicating the development of cardiac muscle hypertrophy. Western blotting with antibodies specific to the N-sequence of rat obscurin previously produced by us revealed a 1.2-fold decrease (p ≤ 0.01) in the content of the A-isoform (880 kDa) of this protein in the left ventricle of the rat heart after isoprenaline injection. This decrease was observed against the background of elevated content (4.2-fold; p ≤ 0.01) of obscurin mRNA. The role of reduced obscurin content in the deterioration of heart function during the development of isoprenaline-induced myocardial injury is discussed.