Protective effects of verapamil against isoprenaline-induced mobilization of mitochondrial calcium and cellular lipid droplets in the myocardium

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Abstract
Calcium level and lipid droplets accumulation is studied in the mouse myocardium of animals receiving a single injection of isoprenaline(ISP), of animals receiving ISP after 4–8 days of pretreatment with verapamil (Isoptin), and, of control animals. The animals are sacrificed 4 h after the ISP-injection. Calcium is determined in isolated mitochondria and in whole tissue homogenates by atomic absorption spectrometry. Lipid droplets accumulation is analysed by quantitative stereological technique. Mitochondrial calcium is raised by 65% and calcium of whole tissue homogenates by 21% following ISP stimulation. At the same time, the myocardial fractional volume occupied by lipid droplets in the ISP treated animals increases to 14 times that of control. The ISP stimulated elevation of mitochondrial calcium is reduced by 73% and that of lipid fractional volume by 71% after pretreatment with verapamil. No similar reduction of calcium content is observed in the whole tissue homogenates. These results are discussed in terms of the role of Ca2+ in ISP induced myocardial necrosis.