Abstract
Previous data has suggested a deleterious action of Amrinone (Am) on newborn (NB) myocardium. An investigation of the relationship between dose, age, and contractility has been undertaken using isolated right ventricular papillary muscles from NB (0-5 days), juvenile (J) (18-29 days), and adult (A) New Zealand white rabbits. At least six rabbits were studied in each age group using four sequential concentrations of Am (30, 100, 200, 500 mcg/ml). Peak tension (PT), maximum rate of tension development (+dP/dt) and maximum rate of relaxation (-dP/dT) were measured after a fifteen minute equilibration period at each concentration. Repeated measures analysis was used to compare dose response data between age groups. T-tests were used to compare normalized data from the various age groups at a given concentration. Adult heart demonstrated an increase in PT, +dP/dt and -dP/dT with each increase in Am concentration. NB and J heart demonstrated a significant (P<0.05) decrease in PT and +dP/dt for only the lowest dose of An. In contrast to NB the lowest dose did not depress -dP/dT In J. Above 200 mcg/ml, NB and J hearts demonstrated a significant (P<0.05) increase in PT, +dP/dt, and -dP/dt. These results suggest that higher concentrations of Am enhance contractility in NB and J myocardium. While the dose dependence of A heart is monotonic, the NB and J response is biphasic, suggesting multiple and age dependent mechanisms of action. The differential effect of Am on -dP/dT In NB and J hearts implies a developmentally determined action of Am on Ca sequestration in addition to its positive inotropic effect.
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Klitzner, T., Degner, T., Ravin, R. et al. NEWER CARDIOTONIC AGENTS – BENEFICIAL EFFECTS ON NEWBORN MYOCARDIUM. Pediatr Res 21 (Suppl 4), 191 (1987). https://doi.org/10.1203/00006450-198704010-00147
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DOI: https://doi.org/10.1203/00006450-198704010-00147