Abstract
Tamm-Horsfall protein (THP) is produced exclusively by renal distal tubular epithelium cells, and is the most abundant urinary protein in healthy subjects. In the Western blot analysis using anti-human THP antibody, THP was detected not only in 100 kD of its molecular mass, but also in 147, 165, 225, and 270 kD. Furthermore, THP-positive bands were detected in the area of high molecular mass above 100 kD. To reveal whether these characteristic bands were based on the THP complex formed by disulfide bond with other proteins, we employed diagonal electrophoresis coupled with mass spectrometric analysis. As a result, the one-dimensional band of 165 kD detected in the non-reduced SDS-PAGE included THP monomer, immunoglobulins γ chain, and κ chain. The other band of 270 kD was composed of THP monomer, immunoglobulins γ chain, κ chain, and α chain. The wide THP-positive area was assigned to monomer THP. These results suggest that urinary THP is excreted into urine in various molecular forms having disulfide linkage with THP itself, IgG or IgA.
