Disruption of tPA gene reduces total collagen accumulated in the obstructed kidney. Total kidney collagen content in the obstructed kidneys in sham-operated mice and at day 3 and day 7 after UUO in tPA+/+ and tPA–/– mice was determined by biochemical assay. Results in various groups are expressed as μg per mg kidney and presented as mean ± SEM (n = 5). **P < 0.01 vs. all other groups. *P < 0.01 vs. tPA+/+ mice.