Evaluation of the mitochondrial respiration of cardiac myocytes in rats submitted to mechanical bile duct obstruction1 Avaliação da respiração mitocondrial de miócitos cardíacos em ratos ictéricos sumetidos à obstrução do ducto biliar

Purpose: The objective of the present study was to evaluate the capacity of the myocardium for energy production by the analysis of mitochondrial respiration in rats with jaundice submitted to bile duct ligature. Methods: Sixteen male Wistar rats were divided into 2 Groups: Group SO submitted to nontherapeutic laparotomy (sham operation) and Group IC (icteric group) submitted to bile duct ligature. After 7 days, laparotomy was again performed in all animals for cardiac muscle extraction and analysis. Mitochondrial oxygen consumption was determined by stage 3 velocity and stage 4 velocity. The respiratory control ratio (RCR) was obtained by the ratio of stage 3 to stage 4 velocity. Statistical analysis was performed by the Mann-Whitney test, with the level of significance set at 5% (p<0.05).Results: Statistical analysis revealed a significant drop in oxygen consumption during stage 3 mitochondrial respiration in group IC compared with SO, whereas the values obtained during stage 4 were basically identical for the two groups. Likewise, RCR values exhibited a significant reduction. Conclusion: The cellular respiration of the “jaundiced heart” is depressed. This was demonstrated by the reduced capacity of cardiac mitochondria to consume oxygen and synthesize ATP, supporting the idea of a latent cardiac impairment responsible for the hemodynamic decompensation occurring during cholestasis.