Nocturnal blood pressure is elevated with natriuresis and proteinuria as renal function deteriorates in nephropathy

doi:doi:10.1111/j.1523-1755.2004.00419.x

Abstract

Nocturnal blood pressure is elevated with natriuresis and proteinuria as renal function deteriorates in nephropathy.

Background

We reported that patients with sodium sensitive type of hypertension exhibited the lack of nocturnal fall in blood pressure with enhanced natriuresis during night. Sodium sensitivity is caused by diminished glomerular filtration capability and/or augmented tubular reabsorption of sodium, and seems tightly linked with glomerular capillary hypertension. In the present study, we investigated the relationship between glomerular filtration rate and circadian rhythms of these parameters in patients with glomerulopathy.

Methods

Twenty six patients (15 men and 11 women; aged 17 to 72 years; mean age 47 plusminus 3 years), whose diagnosis was confirmed as glomerulopathy with renal biopsy, were studied during hospitalization. Ambulatory blood pressure for 24 hours was monitored, while urinary samples were collected for both daytime (6:00 a.m. to 9:00 p.m.) and nighttime (9:00 p.m. to 6:00 a.m.) to estimate circadian rhythms of urinary sodium and protein excretion rates (U_NaV, U_proV). Then night/day ratios of mean arterial blood pressure (MAP), U_NaV, and U_proV were analyzed in relation to 24-hour creatinine clearance as a marker of glomerular filtration rate.

Results

Serum creatinine and creatinine clearance were 1.1 plusminus 0.1 mg/dL and 89 7 mL/min/1.73 m2. There were significant day-night differences in MAP (96 2 mm Hg vs. 92 2 mm Hg; P = 0.006), U_NaV (6.7 0.9 mmol/hour vs. 3.6 0.3 mmol/hour; P = 0.003), and U_proV (161 27 mg/hour vs. 128 28 mg/hour; P = 0.02). Creatinine clearance had significantly negative relationships with night/day ratios of MAP (r=-0.49; P = 0.01), U_NaV (r=-0.43; P = 0.03,) and U_proV (r=-0.41; P = 0.04). In addition, night/day ratio of MAP had significantly positive relationships with night/day ratios of U_NaV (r = 0.49; P = 0.01) and U_proV (r = 0.45; P = 0.02).

Conclusion

Our results show that as renal function deteriorates in glomerulopathy the nocturnal dip in blood pressure is lost, resulting in enhanced urinary sodium and protein excretions during night. These findings are compatible with our proposal that impaired natriuresis during daytime makes nocturnal blood pressure elevated to compensate for diminished natriuresis by pressure natriuresis. We speculate that nocturnal glomerular capillary hypertension contributes, at least in part, to enhanced urinary sodium and protein excretions during night.

Keywords:

circadian rhythm, blood pressure, natriuresis, proteinuria, renal function

Clinical Nephrology – Epidemiology – Clinical Trials