Circadian rhythm and postural change in natriuresis in non-dipper type of essential hypertension

Recently we found that, in non-dipper type of essential hypertensive patien ts who showed the lack of nocturnal fall in blood pressure, circadian rhyth m of urinary sodium excretion rate was disturbed. In the present study we e xamined whether postural change in natriuresis is also disturbed in non-dip pers, Sixteen inpatients with essential hypertension were maintained on a r elatively high sodium diet containing 10 to 12 g of NaCl per day for 8 days , On the 7th day of the study period, 24-h ambulatory blood pressures were measured, and 5-7th days urinary samples were collected for both daytime an d night-time. On the last day of the study period, patients stood for 2 h a nd then lay down for 2 h, Urinary volume and excretion rates of creatinine and sodium were measured every hour in both positions. Night-time urinary s odium excretion rate was significantly higher in non-dippers (n = 9) than t hat in dippers (n = 7), Night/day ratio of mean arterial pressure had a pos itive relationship with night/day ratio of urinary sodium excretion rate. I n non-dippers, but not in dippers, the mean value of U,,V during upright po sition was significantly lower than that during supine position. There was a significantly negative relationship between upright/supine ratio of U,,V and night/day ratio of MAP or night/day ratio of U,,V, In patients with non -dipper type of essential hypertension, both natriuresis patterns, circadia n rhythm and postural change, were disturbed.