ENERGY-METABOLISM PATTERNS IN MAMMALIAN MYOCARDIUM ADAPTED TO CHRONICPHYSIOPATHOLOGICAL CONDITIONS

Objective: When the myocardium is subjected to a chronic overload, it enlarges and a major restructuring of all organelles and cellular func tions occurs. The changes occurring at the level of the contractile ap paratus are well documented; less is known about the alterations in th e energy status of the hypertrophied cardiomyocyte. The purpose of thi s paper is firstly to provide a brief review of the data published on this topic and secondly to analyse previously published data drawn fro m studies devoted to the evaluation of the capacity of the ATP-produci ng processes to respond to an acute change in workload. Methods: Sever al different chronic conditions were studied in rats: senescence, hype rtension, chronic hypoxia, and administration of thyroid hormone. The pattern of the metabolic response of the heart to acute changes in wor kload was characterized by alterations in the concentrations of phosph ocreatine, inorganic phosphate and ATP followed in isolated heart by P -31-NMR spectroscopy. Results: In most of the models studied the patte rn of these changes was very similar to that observed in controls. The only exceptions concerned the hearts of young hypertensive rats and t hose of animals subjected to a cumulated overload (hypertension + thyr oid hormone). Conclusion: Our results demonstrate that the regulation of energy metabolism was well preserved in spite of the extensive rest ructuring that occurs in rat hearts subjected to different chronic con ditions which could affect the energy balance of the cardiomyocyte.