Chloride alters renal blood flow autoregulation in deoxycorticosterone-treated rats

Renal blood flow autoregulation was studied in deoxycorticosterone acetate (DOCA)-treated rats. DOCA pellets (75 mg) were implanted in uninephrectomized rats, and the animals were then fed one of four diets: (1) normal sodium chloride level, (2) high in NaCl, (3) high in chloride, or (4) high in sodium. After 40 to 45 days of the DOCA-diet treatment, animals were subjected to renal blood flow autoregulation experiments; an inflatable aortic occluder was placed proximal to the renal artery, and renal blood flow (electromagnetic flow probe) was measured while renal perfusion pressure was reduced from normal (in that animal) to 20 mm Hg, in 10 mm Hg decrements to determine the lower threshold of autoregulation. Directly measured arterial blood pressure was higher in the DOCA-high NaCl group compared with the DOCA-normal NaCl group (127 +/- 3 mm Hg vs 103 +/- 4 mm Hg) during anesthesia. Significant elevation of lower autoregulatory thresholds were demonstrated in both the DOCA-high NaCl (98 +/- 7 mm Hg) and high chloride groups (94 +/- 3 mm Hg) compared with the DOCA-normal NaCl (77 +/- 4 mm Hg) and the DOCA-high sodium (76 +/- 5 mm Hg). Pressure-flow curves of the DOCA-high chloride groups were shifted significantly downward (reduced renal blood flow at all pressures) and rightward (elevated lower threshold) compared with the DOCA-normal NaCl and -high sodium groups. These data indicate that DOCA-treated rats consuming a diet high in chloride have altered renal blood flow autoregulatory mechanisms.