Renal plasma flow: glomerular filtration rate relationships in man during direct renin inhibition with aliskiren

We examined the relation between change in renal plasma flow (RPF) and change in glomerular filtration rate (GFR) in healthy humans on a low-salt diet during direct renin inhibition with aliskiren. We measured the renal hemodynamic response to acute dosing of 300 mg aliskiren by mouth to 19 healthy normotensive subjects (age, 33 ± 3 years; baseline RPF, 575 ± 23; GFR, 138 ± 14 mL/min/1.73 m²) on a low-sodium diet (10 mmol/day). GFR and RPF were measured by the clearance of inulin and para-aminohippurate. There was a marked increase in average RPF (169 ± 24 mL/min/1.73 m²) and a small rise in average GFR (1.4 ± 5 mL/min/1.73 m²) from baseline in response to aliskiren. There was a clear correlation between the change in RPF and the change in GFR between subjects (r = 0.65; P < .003). A substantial increase in RPF was accompanied by a rise in GFR. Dependence of GFR on RPF was identified in healthy humans after RPF rose significantly with aliskiren. The responsible mechanism likely involves intravascular oncotic pressure along the glomerular capillary resulting in greater surface area available for filtration.