Urinary excretion of transferrin and orosomucoid are increased after acute protein loading in healthy subjects

Background/ Aims: The aim of this study was to elucidate what kind of plasma proteins would change their urinary excretions when the glomerular filtration rate ( GFR) was increased. Methods: We measured urinary excretions of three plasma proteins with different molecular radii ( MR) and isoelectric points ( pI): albumin, orosomucoid ( OM) and transferrin ( Tf), after acute protein loading in healthy subjects. Results: Urinary excretion of OM with more anioic charge and smaller MR than albumin, and Tf with more cationic charge and slightly larger molecular weight than albumin, significantly increased in parallel with increased creatinine clearances after acute protein loading. These renal responses returned to basal levels 9 h after protein ingestion. In contrast, increases in urinary excretion of albumin were not observed. Conclusion: Because these findings could not be explained by changes in either size or charge selectivity of shunt pores in the glomerular capillary wall, it is suggested that urinary excretion of albumin may have a special property that distinguishes it from other plasma proteins and may be a less sensitive marker to reflect changes in renal hemodynamics than the other plasma proteins. Copyright (C) 2005 S. Karger AG, Basel.