Potassium Supplementation Prevents Sodium Chloride Cotransporter Stimulation During Angiotensin II Hypertension

Abstract

Angiotensin II (AngII) hypertension increases distal tubule Na-Cl cotransporter (NCC) abundance and phosphorylation (NCCp), as well as epithelial Na⁺ channel abundance and activating cleavage. Acutely raising plasma [K⁺] by infusion or ingestion provokes a rapid decrease in NCCp that drives a compensatory kaliuresis. The first aim tested whether acutely raising plasma [K⁺] with a single 3-hour 2% potassium meal would lower NCCp in Sprague–Dawley rats after 14 days of AngII (400 ng/kg per minute). The potassium-rich meal neither decreased NCCp nor increased K⁺ excretion. AngII-infused rats exhibited lower plasma [K⁺] versus controls (3.6±0.2 versus 4.5±0.1 mmol/L; P<0.05), suggesting that AngII-mediated epithelial Na⁺ channel activation provokes K⁺ depletion. The second aim tested whether doubling dietary potassium intake from 1% (A1K) to 2% (A2K) would prevent K⁺ depletion during AngII infusion and, thus, prevent NCC accumulation. A2K-fed rats exhibited normal plasma [K⁺] and 2-fold higher K⁺ excretion and plasma [aldosterone] versus A1K. In A1K rats, NCC, NCCpS71, and NCCpT53 abundance increased 1.5- to 3-fold versus controls (P<0.05). The rise in NCC and NCCp abundance was prevented in the A2K rats, yet blood pressure did not significantly decrease. Epithelial Na⁺ channel subunit abundance and cleavage increased 1.5- to 3-fold in both A1K and A2K; ROMK (renal outer medulla K⁺ channel abundance) abundance was unaffected by AngII or dietary K⁺. In summary, the accumulation and phosphorylation of NCC seen during chronic AngII infusion hypertension is likely secondary to potassium deficiency driven by epithelial Na⁺ channel stimulation.