Relationship between cellular ATP, potassium, sodium and magnesium concentrations in mammalian and avian erythrocytes

Intracellular K⁺ Na⁺ ratios of erythrocytes of various mammalian species are known to differ markedly. We have measured ATP, K⁺, Na⁺, Mg²⁺, H₂O contents of erythrocytes of twelve mammalian and three avian species. Our results indicate that the intracellular ATP concentration in erythrocytes of different species is in close positive correlation with the K⁺ Na⁺ ratios (linear correlation coefficient, r = 0.852). Furthermore, ATP levels in erythrocytes of individual sheep with different potassium concentrations correspond with their K⁺ Na⁺ ratios (r = 0.747). Intracellular magnesium concentrations also correlate with ATP concentrations in erythrocytes of different species (r = 0.629) and in different sheep (r = 0.549).