Abstract
Because adenosine triphosphate (ATP) has been established as the source of energy of the active sodium-potassium pump in the membrane of red blood cells (RBC), and further because it has been reported to stimulate adenylate deaminase (AMPDA) and to inhibit 5'-nucleotidase (5 Nase) in the pathway of purine metabolism, we compared the electrolyte concentrations and the activities of adenosine deaminase (ADA) and nucleoside phosphorylase (NP) in serum and RBC between a serum electrolyte disturbance and a RBC enzyme disorder: the former is seen in a hyperkalemia of a 3-year-old boy diagnosed as renal tubular acidosis (RTA) with selective defect in distal potassium excretion (who became the third reported case in the world) : the latter in a high activity of RBC ADA in siblings of hereditary spherocytosis (HS). The boy with the hyperkalemic type of distal RTA showed RBC potassium increases accompanied by serum potassium increases, i.e. hyperkalemia, and normal values in sodium-potassium ratio, which seems correlated to the active cation pump in RBC membrane. Concerning the total activity or capacity in the RBC membrane mechanism, including the active pump, the passive pump, the simple diffusion and the exchange diffusion, the most intensity of Na efflux (RBC sodium<serum sodium) and K influx (RBC potassium >serum potassium) was found in the hemolytic crisis siblings of the HS family, and transiently In the RTA boy during KCI loading. As one of the relevant enzymes believed necessary for the transport of cation and water or the permeability of RBC membrane, RBC NP in children of the HS family showed the higher activity than in their parents or in the RTA boy, whereas, as one of the unrele-vant enzymes, RBC ADA might be wasted possibly by stimulation of ATP in children of the HS family. Additionally, the results in our previous studies and in this paper enable us to speculate that ATP stimulates ADA as well as AMPDA and inhibits NP as well as 5 Nase in the purine metabolic pathway.
