Facteurs de la variation de la fréquence cardiaque maximale: hypothèse «enképhalinique

To try to explain the decrease in maximal heart rate under different situations (ie, chronic hypoxia, ageing, proteino-energetic malnutrition), cardiac concentration and flow of leucine-encephalin peptide in isolated and perfused hearts were studied in rats. The heart leucine-encephalin concentration which was 301 ± 60 fmol/g before perfusion, increased up to 543 ± 125 fmol/g after perfusion (1 h). The total release during perfusion was four times the initial concentration. Concerning the antagonism of leucine-encephalin on cardiotropic adrenergic effects on isolated cardiomyocytes, it is possible to propose this mechanism to explain totally or partially the decrease in maximal heart rate under particular situations.