Comparative Properties of High Potassium and Low Potassium Sheep Erythrocyte Membrane Sodium-activated Adenosine Triphosphatase

There are two types or sheep distinguished by the intracellular potassium level or their red blood cells, i.e. low potassium red cells and high potassium red cells. Studies by other investigators have shown that both the rate or active sodium and potassium transport and sodium- plus potassium-stimulated adenosine triphosphate hydrolysis (Na+,K+-ATPase) are approximately four times greater in high potassium than in low potassium red cells. In the present study, the sodium-stimulated adenosine triphosphatase (Na+-ATPase) enzyme system in fragmented membrane of the two cell types was compared. For HK:LK activity, the approximate activity ratios were 10 for Na+-stimulated ATPase (Na+-ATPase), 12 for Na+- plus K+-stimulated ATPase (Na+~K+-ATPase), and 2 for Na+-dependent (14C)ADP-ATP exchange; the ratio of Na+-stimulated membrane phosphorylation determined with γ-32P-ATP, was approximately 7.