Reports describing trials of exchange resins in removing cations from the gastrointestinal tract of experimental animals have been limited to toxicity studies and to measurements of the relative magnitudes of the oral intake and the stool output (1-3). In the experiments presented in this paper changes in serum, urine, and stool components, as well as the external and internal balances of certain electrolytes and of nitrogen have been determined in dogs receiving a carboxylic cation exchange resin in one of two forms. The chemical and physical characteristics of these agents have been described in detail in the introductory paper (4).
MATERIALS AND METHODSMongrel female dogs, maintained on a commercial feed ("Friskies") 1 and allowed free access to water, received a carboxylic cation exchange resin in the hydrogen or the sodium form for periods of seven to 11 days. In some instances beef extract or milk and sugar were used to enhance palatability, but many animals nonetheless lost weight partly or entirely as a consequence of anorexia induced by the regimens employed. Since this occurred to an equal degree when control and recovery periods of comparable length were alternated with resin periods it represented a common denominator in our experiments. The beginning and the end in each interval of the study were marked by catheterization of the urinary bladder, measurement of body weight and withdrawal of venous blood for analysis of blood nonprotein nitrogen (NPN) and sugar, and of serum carbon dioxide content, chloride, sodium, potassium, calcium, phosphorus and water, using previously described methods (5-7). The pH of anaerobic samples of serum was determined by means of the glass electrode. Food and resin intake, stool and urine output as well as any vomitus or rejected food were collected, measured, and analyzed separately for nitrogen, sodium, potassium and chloride content (8-10). Stools were removed from the cage and weighed immrediately. Procedures for partitioning the external balances into extracellular and cellular components have been described only in part in previous publications (11)(12)(13)(14)(15)(16)(17) and are therefore appended in detailed form.1 Content per 100 g.: Na, 17.6 meq.; K, 10.2 meq.; Cl, 162 meq.; and N, 3.42 g.With but minor exceptions all findings have been subjected to conventional statistical analyses (18). In the case of the body weight and the serum constituents values observed at the end of each control, experimental, or recovery interval were subtracted from those present at the start of the particular period under scrutiny and expressed as increments or decrements (±t A). After the means of these changes had been calculated (values greater than 2 S. D. were discarded) the resin and post resin values were compared with those of the control periods. Changes were considered significantly different statistically when "p" for the "t" test was 0.05 or less. Urinary and stool output and the balance data were analyzed in terms of per diem values.