Dietary sodium intake does not alter renal potassium handling and blood pressure in healthy young males

BACKGROUND: The effects of sodium (Na(+)) intakes on renal handling of potassium (K(+)) are insufficiently studied. METHODS: We assessed the effect of Na(+) on renal K(+) handling in 16 healthy males assigned to three 7-day periods on low salt diet [LSD, 3 g sodium chloride (NaCl)/day], normal salt diet (NSD, 6 g NaCl/day) and high salt diet (HSD, 15 g NaCl/day), with constant K(+) intake. Contributions of distal NaCl co-transporter and epithelial Na(+) channel in the collecting system on K(+) and Na(+) handling were assessed at steady state by acute response to 100 mg oral hydrochlorothiazide and with addition of 10 mg of amiloride to hydrochlorothiazide, respectively. RESULTS: Diurnal blood pressure slightly increased from 119.30 ± 7.95 mmHg under LSD to 123.00 ± 7.50 mmHg (P = 0.02) under HSD, while estimated glomerular filtration rate increased from 133.20 ± 34.68 mL/min under LSD to 187.00 ± 49.10 under HSD (P = 0.005). The 24-h K(+) excretion remained stable on all Na(+) intakes (66.28 ± 19.12 mmol/24 h under LSD; 55.91 ± 21.17 mmol/24 h under NSD; and 66.81 ± 20.72 under HSD, P = 0.9). The hydrochlorothiazide-induced natriuresis was the highest under HSD (30.22 ± 12.53 mmol/h) and the lowest under LSD (15.38 ± 8.94 mmol/h, P = 0.02). Hydrochlorothiazide increased kaliuresis and amiloride decreased kaliuresis similarly on all three diets. CONCLUSIONS: Neither spontaneous nor diuretic-induced K(+) excretion was influenced by Na(+) intake in healthy male subjects. However, the respective contribution of the distal convoluted tubule and the collecting duct to renal Na(+) handling was dependent on dietary Na(+) intake.