Association between heparan sulfate proteoglycan excretion and proteinuria after renal transplantation

Abstract

The aim of the study presented here was to investigate whether in patients showing immediate graft function after renal transplantation, cold- ischemia and reperfusion lead to damage of the glomerular basement membrane and consequently to a loss of heparan sulfate proteoglycans. Loss of these heparan sulfate proteoglycans is a major cause of proteinuria. Time-dependent changes in urinary excretion rates of heparan sulfate proteoglycans but also of total protein, albumin, low- and high-molecular-weight proteins were analyzed quantitatively and by polyacrylamid-gel-electrophoresis in eight patients. Immediately after renal transplantation, severe proteinuria with an excretion rate at up to 251 ± 108 mg/min was apparent and rapidly declined within 24 h to 4.11 ± 2.80 mg/min. The gel-electrophoretic pattern showed a nonselective glomerular and tubular proteinuria. The excretion rate of heparan sulfate proteoglycan was increased in this initial reperfusion phase (up to 7 h), most probably because of ischemia- and reperfusion-induced damage of the glomerular basement membrane. The initial nonselective glomerular proteinuria disappeared within 48 h, changing to a mild selective glomerular proteinuria. In this second phase (7 to 48 h), lower levels of heparan sulfate proteoglycan excretion were observed (0.54 ± 0.54 μg/min versus 1.66 ± 1.93 μg/min, P < 0.05). However, during the repair process of the glomerular basement membrane, heparan sulfate proteoglycan is synthesized de nova, leading to an increasing heparan sulfate proteoglycan content of the glomerular basement membrane. This second phase is paralleled by the change from o nonselective to a selective glomerular proteinuria. In the third phase, when the heparan sulfate proteoglycan content of the glomerular basement membrane normalizes, glomerular proteinuria was abolished in most of the patients.