Role of Na⁺-Ca²⁺ exchange in neonatal and adult ventricular cells: A simulation study

The Na⁺-Ca²⁺ exchange assumes considerable importance in neonatal cells with a morphologically sparse sarcoplasmic reticulum. Our simulation shows that the neonatal ventricular cell consumed larger amount of ATP than the adult ventricular cell, owing to a long relaxation time. The amount of ATP consumed per beat was reduced to the amount equivalent to the adult ventricular cells, thus increasing the relative current density of Na ⁺-Ca²⁺ exchange by 4-fold, which is consistent with the observed current density in the neonatal rabbit ventricular cells.