Deficiency of tPA preserves the functional integrity of TBM in the obstructed kidneys. TBM functional integrity was determined by bacterial translocation across the reconstituted TBM. (a) Schematic depiction of experimental procedures. Matrigels (15 μm thick) analogous to native TBM matrix were formed on Transwell filters and incubated with whole-tissue lysates of the obstructed kidneys collected 7 days after UUO from tPA^+/+ and tPA^–/– mice. The integrity of the Matrigels was assessed by bacterial translocation through the gels. Representative plates show the colonies formed from the bacteria that passed through the Matrigels after incubation with tissue extracts from either tPA^+/+ (b) or tPA^–/– (c) mice. (d) Graphic presentation of the numbers of bacteria translocated through the Matrigels (n = 5). *P < 0.01 vs. tPA^+/+ mice. (e) Zymographic analysis shows the specificity of MMP-9 inhibitor. Tissue lysates from the obstructed kidneys of either tPA^+/+ or tPA^–/– mice were separated on a polyacrylamide gel containing 1 mg/ml gelatin. A potent MMP-9 inhibitor (MMP inhibitor II) was included in the developing buffer at a concentration of 10 nM. The locations of bands corresponding to MMP-9 and MMP-2 are indicated. Numbered lanes indicate two animals per group. (f) Graphic presentation of the numbers of bacteria translocated through Matrigels preincubated with kidney lysates in the presence of 10 nM MMP-9 inhibitor. No statistically significant difference was found between tPA^+/+ and tPA^–/– groups.