Effect of dietary chloride on spontaneously hypertensive rat

The anionic component of sodium salt has been reported to contribute to hypertension in some animal models and hypertensive patients. In the present study, the anionic effects on exacerbation of hypertension in spontaneously hypertensive rat (SHR) were investigated by chronic loading tests with two sources of sodium, viz. sodium chloride (NaCl; 0.9% solution) and sodium bicarbonate (NaHCO3; 1.28% solution), using SHRs with normal renal function (NRF) and with chronic renal failure (CRF; produced by cryosurgery). In addition, extracellular fluid volume (ECFV: inulin space) was measured in SHRs with NRF and CRF. In the NRF groups, systolic blood pressure (SBP) reached 230 mmHg at Week 13, and there was no significant difference in SBP between the NaCl and NaHCO3 groups. In the CRF groups, SBP of the NaCl group was significantly higher (p less than 0.01) than that of the NaHCO3 group (280 mmHg vs. 230 mmHg at Week 15). ECFV was also greater in the NaCl group than in the NaHCO3 group (ECFV: NaCl vs. NaHCO3, 15.9 +/- 1.7 vs. 14.0 +/- 0.9 at Week 13; and 16.2 +/- 1.1 vs. 14.2 +/- 1.2 at Week 15, respectively). These results indicate that chloride ion plays an important role in the pathogenesis of hypertension in SHR with CRF. Expansion of ECFV is considered to be one of the mechanisms whereby the hypertension is exacerbated.