Effects of an Acute Protein Load in Comparison to an Acute Load of Essential Amino Acids on Glomerular Filtration Rate, Renal Plasma Flow, Urinary Albumin Excretion and Nitrogen Excretion

Abstract

Pre- and postprandial changes of inulin and PAH clearance, urinary albumin excretion and nitrogen excretion after an acute load of 1.4 g/kg body-weight of essential aminoacids (EAA) were compared to the changes after a load of the same amount of proteins in ten healthy subjects. Six of the volunteers underwent the same procedure in a third set of experiments, receiving only a water load instead of a test meal (control group). Inulin clearance showed a maximal increase of 27.6 +/- 2.3% after the EAA load, compared to 31.7 +/- 3.8% after the protein load. Parallel to the increase in inulin clearance, PAH clearance increased to 34.1 +/- 3.8% (EAA) compared to 35.5 +/- 3.4% (proteins). Urinary nitrogen excretion increased from a preprandial value of 8.7 +/- 1.6 mg/min to a postprandial value of 13.7 +/- 3.5 mg/min after the EAA load, while it increased after the protein load from 8.1 +/- 3.1 mg/min to 15.4 +/- 3.3 mg/min. Urinary albumin excretion increased from a preprandial value of 4.8 +/- 1.7 microg/min to a maximum of 13.5 +/- 4.7 microg/min after the EAA load. After the protein load the albumin excretion increased to maximum of 14.4 +/- 5.4 microg/min. Increased albumin excretion was associated with an increase in diuresis. Comparing both test meals, the only significant difference was observed in the postprandial values of urinary nitrogen excretion. In the control group inulin and PAH clearance and urinary nitrogen excretion did not change significantly after the water load, while parallel to an increase in postprandial diuresis urinary albumin excretion increased to a maximum of 11.6 +/- 5.1 microg/min. In comparison to the control group urinary albumin excretion was significantly greater 120-180 min after both test meals, although no significant difference was observed in urinary flow.