Effect of protein-restricted diet on renal response to a meat meal in humans

To study the influence of preceding dietary protein intake on the renal response to a protein meal we examined renal hemodynamic and excretory responses to a meat meal in six normal human subjects either taking their normal-protein diet (NPD, 75 +/- 5 g/day) or after 3 wk of a low-protein diet (LPD, 43 +/- 3 g/day; P less than 0.005). Glomerular filtration rate (GFR) was lower on LPD than on NPD (107 +/- 7 vs. 124 +/- 5 ml X min-1 X 1.73 M-2, respectively; P less than 0.01), as was renal plasma flow (RPF) (NPD, 666 +/- 44; LPD, 605 +/- 43 ml X min-1 X 1.73 M-2; P less than 0.05). Filtration fraction (FF) was not different (NPD, 0.19 +/- 0.01; LPD, 0.18 +/- 0.01). Urinary excretion of albumin was also lower after LPD than NPD (2.1 +/- 0.5 vs. 4.2 +/- 0.8 micrograms/min; P less than 0.05). After an 80-g protein meat meal, GFR rose to a ceiling significantly higher on NPD than on LPD (132 +/- 4.8 vs. 120 +/- 5.2 ml X min-1 X 1.73 M-2; P less than 0.02), even though the percent changes were greater on LPD than on NPD (12.7 +/- 3.3 vs. 6.6 +/- 1.5%, respectively; P less than 0.05). There was a rise in RPF that was entirely attributable to a fall in renal vascular resistance, and FF did not change. On both diets, oral protein loading produced a 200-300% increase in the urinary excretion and fractional clearance of albumin and IgG, but failed to alter that of beta 2-microglobulin.(ABSTRACT TRUNCATED AT 250 WORDS)