Quantitative and qualitative evaluation of plasma and urine α1-microglobulin in healthy donors and patients with different haemolytic disorders and haemochromatosis

BackgroundThe haem-binding protein α1-microglobulin (α1m) is involved in protection against oxidative damage induced by extracellular haem/haemoglobin. A carboxy-terminally truncated form of α1m (t-α1m), formed by reactions with haemoglobin, degrades haem into a yellow–brown chromophore linked to the protein. The aim of this work was to investigate if t-α1m is present in urine from a large cohort and if urinary and plasma α1m/t-α1m concentrations are changed in patients with haemolytic disorders and haemochromatosis.MethodsUrine and blood from patients (n = 20) and a control group (n = 22) were investigated for α1m and t-α1m by gel electrophoresis, Western blotting and radioimmunoassay. Data were compared to clinical chemistry data and medical records.ResultsTwo thirds of all studied subjects displayed t-α1m in urine but the t-α1m/α1m ratio was not increased in patients. Instead, significantly elevated ratios were found in females compared to males. Patients with intravascular or extravascular haemolysis showed higher α1m, albumin and β2-microglobulin/creatinine ratios in urine indicating glomerulo-tubular dysfunction.ConclusionsThe demonstration of t-α1m in urine of this cohort may be of importance in quantitative clinical chemistry. Whilst impaired kidney function due to intravascular haemolysis is well-known to occur, it is an unexpected finding in a group of patients with extravascular haemolysis.