Sodium-, potassium-, chloride-, and bicarbonate-related effects on blood pressure and electrolyte homeostasis in deoxycorticosterone acetate-treated rats

Na+ loading without Cl- fails to increase blood pressure in the DOCA model. We compared the changes in the total body (TB) effective Na+, K+, Cl-, and water (TBW) content as well as in intracellular (ICV) or extracellular (ECV) volume in rats receiving DOCA-NaCl, DOCA-NaHCO3, or DOCA-KHCO3. We divided 42 male rats into 5 groups. Group 1 was untreated, group 2 received 1% NaCl, and groups 3, 4, and 5 were treated with DOCA and received 1% NaCl, 1.44% NaHCO3, or 1.7% KHCO3 to drink. We measured mean arterial blood pressure (MAP) directly after 3 wk. Tissue electrolyte and water content was measured by chemical analysis. Compared with control rats, DOCA-NaCl increased MAP while DOCA-NaHCO3 and DOCA-KHCO3 did not. DOCA-NaCl increased TBNa+ 26% but only moderately increased TBW. DOCA-NaHCO3 led to similar TBNa+ excess, while TBW and ICV, but not ECV, were increased more than in DOCA-NaCl rats. DOCA-KHCO3 did not affect TBNa+ or volume. At a given TB(Na+ + K+) and TBW, MAP in DOCA-NaCl rats was higher than in control, DOCA-NaHCO3, and DOCA-KHCO3 rats, indicating that hypertension in DOCA-NaCl rats was not dependent on TB(Na+ + K+) and water mass balance. Skin volume retention was hypertonic compared with serum and paralleled hypertension in DOCA-NaCl rats. These rats had higher TB(Na+ + K+)-to-TBW ratio in accumulated fluid than DOCA-NaHCO3 rats. DOCA-NaCl rats also had increased intracellular Cl- concentrations in skeletal muscle. We conclude that excessive cellular electrolyte redistribution and/or intracellular Na+ or Cl- accumulation may play an important role in the pathogenesis of salt-sensitive hypertension.