Does high salt intake cause hyperfiltration in patients with essential hypertension?
In animal models of salt-dependent hypertension, hyperfiltration is associated with a faster decline in renal function and there is evidence that in hypertensive man, increased creatinine clearance is a marker of early hypertensive nephropathy. We have studied the influence of salt intake on the glomerular filtration rate (GFR) (Creatinine Clearance) in 14 patients with mild hypertension. Each patient was studied in random order and according to a crossover design, at habitual salt intake, at high salt intake (ie habitual +50/100 mmol/day) and at low salt intake (habitual -50/100 mmol/day). Protein, calcium and potassium intake was fixed across the three study periods. The control group was formed by seven healthy subjects. High salt intake, caused a significant (P < 0.01) increase in 24 h mean arterial pressure (MAP) and the expected suppression in plasma renin activity (PRA) and in plasma aldosterone. Seven patients were classified as salt-sensitive. The GFR was significantly higher
