Red cell magnesium in rainbow trout
In vivo erythrocytic magnesium concentration was significantly correlated with red cell potassium level and potassium equilibrium potential, but not with specimen weight, plasma magnesium, red cell sodium and chloride, or chloride equilibrium potential. To examine the relationship between magnesium and potassium, potassium levels were manipulated in vitro with catecholamine, furosemide, ouabain, and valinomycin. Over a wide range of normal and supranormal potassium concentrations, a significant correlation between magnesium and potassium levels was evident. However, depletion of potassium following exposure to ouabain and valinomycin led to a shift from the normal high potassium/low sodium relationship to a high sodium/low potassium state with progressive increases in magnesium content. Correlation of magnesium with potassium was lost, and a significant correlation with red cell sodium, but not with sodium equilibrium potential, was evident. Red cell magnesium concentration appears, therefore, to be influenced by the preponderant univalent cellular cation rather than potassium per se.