TBM structural integrity is largely preserved in the obstructed kidneys in tPA^–/– mice. TBM structural integrity was examined by immunofluorescence staining of laminin, the major component of TBM. (a–e) Representative micrographs show the TBM (red) and tubular cells (green) in obstructed kidneys at 7 days after UUO in tPA^+/+ (a–c) and tPA^–/– (d and e) mice. Renal proximal tubules were stained with lectin from T. purpureas (green). The TBM in the kidney of tPA^+/+ mice is displayed as severely impaired, broken, and interrupted (arrowheads), whereas TBM structural integrity was largely preserved in tPA^–/– mice. Images in b and c are enlarged from the boxed areas in a, and e is an enlargement of the boxed area in d. Arrowheads indicate the broken TBM. Scale bar in a and d: 20 μm; scale bar in b, c, and e: 10 μm. (f) Graphic presentation of the percentages of renal tubules with TBM lesions in the cortical region of obstructed kidneys in tPA^+/+ and tPA^–/– mice. The data were calculated based on individual values determined on ten fields per mouse, five mice per group (n = 5). *P < 0.01 vs. tPA^+/+ mice.