Fig. 2. Fluid intake of rats subjected to KCl or NH4Cl loading in a pair-drinking protocol. Rats were placed in metabolic cages with free access to food and water. After 3 days and at time 0, the animals were switched to a drinking solution containing 280 mM KCl. The access to KCl solution is, however, limited to the same volume of NH4Cl solution taken by NH4Cl-loaded rats that was determined daily during the NH4Cl-loading protocol (Fig. 1). *P < 0.002 vs. baseline for both KCl- and NH4Cl-loaded rats; n = 8 rats before and n = 4 rats after 24 h for KCl loading; n = 13 rats before and n = 7 rats after 24 h of NH4Cl loading. DOI: (10.1152/ajprenal.00338.2005)