Two days after high K+ intake, Rrbp1-KO mice had higher serum potassium levels (8.53 ± 0.38 versus 7.23 ± 0.27 mmol/L; P = 0.0086), decreased transtubular potassium gradient (TTKG) (14.62 ± 0.79 versus 18.44 ± 1.04; P = 5.8 × 10−3), and lower urine fractional excretion of potassium (43.14 ± 4% versus 64.84 ± 6.7%; P = 8.1 × 10−3) than Rrbp1-WT mice (Table 3), indicating that Rrbp1-KO mice developed hyporeninemic hypoaldosteronism with hyperkalemia. The gene discussed is RRBP1; the disease is Hyperkalemia.