Does high salt intake cause hyperfiltration in patients with essential hypertension?

Area of Science:

• Nephrology
• Cardiovascular Medicine
• Hypertension Research

Background:

• Hyperfiltration in animal models of salt-dependent hypertension correlates with renal function decline.
• Increased creatinine clearance in humans with hypertension may indicate early hypertensive nephropathy.

Purpose of the Study:

• To investigate the impact of varying salt intake on glomerular filtration rate (GFR) in patients with mild hypertension.
• To determine if salt intake influences GFR independently of arterial pressure and the renin-aldosterone system.

Main Methods:

• A crossover study design was used with 14 mild hypertension patients and 7 healthy controls.
• Patients underwent three periods: habitual, high (habitual +50/100 mmol/day), and low (habitual -50/100 mmol/day) salt intake.
• Glomerular filtration rate (GFR) was assessed via creatinine clearance, alongside 24-hour mean arterial pressure (MAP), plasma renin activity (PRA), and plasma aldosterone levels.

Main Results:

• High salt intake significantly increased GFR (125 ± 10 ml/min) compared to habitual (113 ± 7 ml/min) and low salt intake (97 ± 6 ml/min) in hypertensive patients.
• Urinary salt excretion strongly correlated with GFR (P < 0.01), with a 100 mmol/day salt increase associated with a 14.6 ml/min GFR rise.
• The GFR response to salt loading was largely independent of the renin-aldosterone system, and no changes were observed in healthy subjects.

Conclusions:

• In mild hypertension, physiological variations in salt intake significantly alter GFR.
• High salt intake, independent of blood pressure effects, may contribute to kidney damage (nephronic obsolescence) in essential hypertension.
• Monitoring and managing salt intake is crucial for preserving renal function in hypertensive individuals.