CIRCADIAN-RHYTHM OF ARTERIAL BLOOD-PRESSURE AND ALBUMINURIA IN DIABETIC NEPHROPATHY

The aim of our study was to evaluate the diurnal relationship between arterial blood pressure and albuminuria, and some potential mechanisms responsible for impaired nocturnal blood pressure reduction (non-dipp ers, groups I and II) in diabetic nephropathy (DN). Twenty-four-hour a mbulatory blood pressure, heart rate (HR) variation (autonomic nervous function) and extracellular fluid volume (ECV) were measured, and uri ne samples were collected three times during the corresponding day- an d nighttimes in 47 insulin-dependent diabetic (IDDM) patients with DN. Mean arterial blood pressure (MABP) during the daytime [mm Hg, median (range)] was identical in group I [105 (96-137)], group II [109 (86-1 24)] and group III [dippers; average blood pressure reduction from day to night > 10%, 107 (93-132),P = NS], while the nighttime MABP differ ed [group I, 106 (95-144); group II, 100 (78-118); group III, 91 (76-1 18); P < 0.001]. No significant difference between the groups concerni ng the daytime or nighttime albuminuria [mu g/min; median (range)] was observed; [Day: group I, 1467 (235-3933); group II, 695 (170-6719); g roup III, 875 (228-3173). Night: group I, 1079 (279-4665); group II, 5 72 (113-3807); group III, 659 (81-2493)]. A significant correlation be tween MABP and albuminuria was demonstrated during day- (rho = 0.50, P < 0.0005) and nighttime (rho = 0.46, P < 0.005), while neither the ab solute nor the relative changes in MABP from day to night correlated s ignificantly with absolute or relative changes in albuminuria from day to night. The night/day ratio of HR was higher in group I [0.93 (0.76 -1.09), median (range)] compared to group III [0.83 (0.74-1.02), P < 0 .005] and a significant correlation between this ratio and the night/d ay ratio of MABP was found (rho = 0.54, P < 0.0005). ECV was about the same in the three groups. Our study indicated an association between blood pressure and albuminuria, but the mechanisms involved in the red uction of albuminuria from day to night was not unraveled. A relative lack of sympathetic withdrawal during sleep seems to be an important f eature of nocturnal hypertension in diabetic nephropathy.