Circadian rhythm of urinary potassium excretion during treatment with an angiotensin receptor blocker

Introduction: We have reported that the circadian rhythm of urinary potassium excretion (UKV) is determined by the rhythm of urinary sodium excretion (UNaV) in patients with chronic kidney disease (CKD). We also reported that treatment with an angiotensin receptor blocker (ARB) increased the UNaV during the daytime, and restored the non-dipper blood pressure (BP) rhythm into a dipper pattern. However, the circadian rhythm of UKV during ARB treatment has not been reported. Materials and methods: Circadian rhythms of UNaV and UKV were examined in 44 patients with CKD undergoing treatment with ARB. Results: Whole-day UNaV was not altered by ARB whereas whole-day UKV decreased. Even during the ARB treatment, the significant relationship persisted between the night/day ratios of UNaV and UKV (r=0.56, p<0.0001). Whole-day UKV/UNaV ratio (p=0.0007) and trans-tubular potassium concentration gradient (p=0.002) were attenuated but their night/day ratios remained unchanged. The change in the night/day UKV ratio correlated directly with the change in night/day UNaV ratio (F=20.4) rather than with the changes in aldosterone, BP or creatinine clearance. Conclusions: The circadian rhythm of UKV was determined by the rhythm of UNaV even during ARB treatment. Changes in the circadian UKV rhythm were not determined by aldosterone but by UNaV.