ELECTROLYTE AND ACID-BASE BALANCE DURING ACUTE LOADING WITH RUBIDIUM CHLORIDE*†

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Abstract
Electrolyte and acid-base balance studies were carried out on normal rats fed 40 meq/kg of RbCl over a period of 2 days and the results compared with those resulting from an equivalent load of KC1. Loading with KC1 resulted in little or no change in electrolyte balance or plasma CO2 content. By contrast, feeding with RbCl resulted in cellular accumulation of approximately 29 meq/kg of Rb and simultaneous renal loss of approximately 28 meq/kg of K and 5 meq/kg of Na. When corrected for the negative balance during the control period, net K loss during Rb loading amounted to approximately 22 meq/kg. These renal losses seemed largely to represent the displacement of intracellular cation by Rb. The administration of Rb also produced a severe extracellular metabolic acidosis which was not accompanied by increased urinary excretion of acid. There was, instead, a slight reduction in ammonium excretion. Thus it would appear that defective renal compensation plays an important role in the maintenance of acidosis in Rb-substituted rats.