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Obesity is a risk factor for arterial hypertension. We studied the relationshi ps between the body mass index(BMI) and the nycthemeral pattern of blood pressur e (BP), renal function and sodium and water excretion (EX) in a group of 25 mode rately hypertensive untreated men (41±2 y, 80±3 kg). Subjects were given a hig h sodium diet (6 g NaCl added to their usual diet, daily EX=200 mmol). On the 7t h day, BP was monitored during 24 h and urine collected in 2 fractions (day=D, 8 :00-22:00 and night=N, 22:00-8:00). Subjects were a posteriori divided into 2 groups according to th e median BMI (26 kg/m2): Group 1, n=12, BMI 23.2±0.6 (mean±SEM) and Group 2, n =13, BMI 29.2±0.5 kg/m2. No difference was observed between the two groups for age, 24 h urine and sodium EX, or systolic and diastolic BP. However, heart rate was significantly higher during N in Group 2 (66±2 vs. 57±2 b/min, p=0.012). Na and water EX were significantly higher during D than during N in Group 1, but lower during D than during N in Group 2. Creatinine clearance was higher in Gro up 2 than in Group 1 especially during N (D+29%, p=0.013; N+49%, p< 0.001). In Group 2, subjects concentrated their urine more than in Group 1, as evaluated from the urine/plasma creatinine ratio (+49%, p=0.019). This ratio was positi vely correlated to BMI during D (r=0.561, p=0.004) but not during N. These resul ts show that the glomerular hyperfiltration associated with overweight is more i ntense at night and that moderately overweight hypertensives have a reduced sodi um and water EX during the day and a compensatory larger EX at night. The reduce d diurnal EX goes along with an increased urine concentration. The nocturnal ris e in EX is concomittant with a rise in heart rate. Given the growing health prob lems linked to obesity and hypertension, these results open a new field for the understanding of the difficulty to excrete sodium in this condition.
Obesity is a risk factor for arterial hypertension. We studied the relationshi ps between the body mass index (BMI) and the nycthemeral pattern of blood pressur e (BP), renal function and sodium and water excretion (EX) in a group of 25 mode Subjects were given a hig h sodium diet (6 g NaCl added to their usual diet, daily EX = 200 mmol). On the 7th h day, BP was monitored (41 ± 2 y, 80 ± 3 kg) during 24 h and urine collected in 2 fractions (day = D, 8:00 - 22:00 and night = N, 22:00 - 8:00). Subjects were a posteriori divided into 2 groups according to the median ems BMI ( 26 kg / m 2): Group 1 n = 12, BMI 23.2 ± 0.6 (mean ± SEM) and Group 2 n = 13, BMI 29.2 ± 0.5 kg / m 2 No difference was observed between the two groups for age 24 h urine and sodium EX, or systolic and diastolic BP. However, the heart rate was significantly higher during N in Group 2 (66 ± 2 vs. 57 ± 2 b / min, p = 0.012). Na and water EX were significantly higher during during D than during N in Group 1, but lower during D than during N in Group 2. Creatinine clearance was higher in Gro up 2 than in Group 1 especially during N (D + 29%, p = 0.013; N + 49%, p <0.001). In Group 2, subjects concentrated their urine more than in Group 1, as evaluated from the urine / plasma creatinine ratio (+ 49%, p = 0.019). This ratio was positi vely correlated to BMI during D (r = 0.561, p = 0.004) but not during. These resul ts show that the glomerular hyperfiltration associated with overweight is more i ntense at night and that moderately overweight hypertensives have a reduced sodi um and water EX during the day and a compensatory larger EX at night. The reduce d diurnal EX goes along with an increased urine concentration. The nocturnal ris e in EX is concomittant with a rise in heart rate. Given the growing health prob lems linked to obesity and hypertension, these results open a new field for the understanding of the difficulty to excrete sodium in this condition.