A Method for the Study of Cation Transport in vivo: Effects of Digoxin Administration and of Chronic Renal Failure on the Disposition of An Oral Load of Rubidium Chloride

Abstract

Cation transport was studied in vivo by measuring the changes in plasma and intraerythrocytic Rb concentrations following an oral load of Rb. The changes in plasma Rb concentration are related to the distribution of Rb to all the body [human] tissues and the changes in intra-erythrocytic Rb concentrations provide an example of Rb uptake by 1 particular tissue. In 8 healthy volunteers pretreatment with a loading dose of digoxin (20 .mu.g/kg) enhanced the rise in plasma Rb concentrations and attenuated the rise in intra-erythrocytic Rb concentrations after the oral load of RbCl. Ten patients with chronic renal failure, compared with a well-matched control group, were found to have changes similar to, but more marked than, those caused by digoxin, i.e. a much greater rise in plasma Rb concentrations and a much smaller rise in intra-erythrocytic Rb concentrations, after the oral load of RbCl. These findings are consistent with widespread reduction in Na+,K+-ATPase activity in subjects who have taken a loading dose of digoxin and patients with chronic renal failure. The findings of previous studies in vitro are supported.