Key result
High-salt diet drives hypertension and reduces GFR by ~28% in salt-sensitive rats.
Why the study?
Does a high-salt diet reduce glomerular filtration rate in conscious Dahl salt-sensitive rats?
Does a high-salt diet reduce glomerular filtration rate in conscious Dahl salt-sensitive rats?
In Dahl salt-sensitive rats, high-salt diet-induced hypertension precedes the reduction in glomerular filtration rate, which can be accurately tracked using a novel noninvasive transcutaneous device.
Answers are grounded in this paper and cite their sources.
High-salt diet may induce sequential hypertension then GFR loss in salt-sensitive rats; leaves open translation to human hypertensive nephropathy.
Sequential changes in glomerular filtration rate during development of hypertension in the conscious Dahl salt-sensitive rats were determined using a new method for measurement. Using a miniaturized device, disappearance curves of fluorescein isothiocyanate-sinistrin were measured by transcutaneous excitation and real-time detection of the emitted light through the skin. Rats with implanted femoral venous catheters (dye injection and sampling) and carotid catheters (mean arterial pressure by telemetry) were studied, while maintained on a 0.4% NaCl diet and on days 2, 5, 7, 14, and 21 after switching to 4.0% (high-salt [HS]) diet. A separate group of rats were maintained on 0.4% for 21 days as a time control. Mean arterial pressure rose progressively from the last day of 0.4% (130±2 mm Hg) reaching significance by day 5 of HS and averaged 162±7 mm Hg by day 21. Urine albumin excretion was significantly elevated (×3) by day 7 of HS in Dahl salt-sensitive rats. Glomerular filtration rate reduced on day 14 of HS falling from 1.53±0.06 mL/min per 100 g body weight to 1.27±0.04. By day 21, glomerular filtration rate had fallen 28% to 1.1±0.04 mL/min per 100 g (t(1/2) 28.4±1.1 minute.) No significant reductions of creatinine clearance were observed throughout the study in response to HS demonstrating the insensitivity of creatinine clearance measurements even with creatinine measured using mass spectrometry. We conclude that the observed reduction of glomerular filtration rate was a consequence and not a cause of the hypertension and that this noninvasive approach could be used in these conscious Dahl salt-sensitive rats for a longitudinal assessment of renal function.
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Cowley et al. (2013) studied Salt-sensitive hypertension (n=15). High-salt diet (4.0% NaCl) with transcutaneous FITC-sinistrin GFR monitoring vs. 0.4% NaCl diet (time control) was evaluated on Glomerular filtration rate (GFR) at day 21 (mL/min per 100 g body weight) (28% reduction from baseline (1.53 to 1.1 mL/min/100 g), p=<0.05). High-salt diet in conscious Dahl salt-sensitive rats increased mean arterial pressure by day 5 and subsequently reduced GFR by 28% by day 21.
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