Quantitative analysis of UUO-induced renal interstitial collagen expression in B2^–/– knockout mice, kallikrein transgenic rats, and B2 receptor antagonist–treated wild-type mice. (a) Collagen expression in obstructed kidneys from B2^+/+ and B2^–/– mice after different periods of ureteral obstruction (3 hours to 14 days). Data are expressed as the mean ± SD percentage of the interstitial area stained; n = 10; *P < 0.05 compared with respective B2^+/+ (same time of obstruction). (b) Representative photographs of Sirius red–stained renal sections of 5 day–obstructed and sham-operated B2^+/+ and B2^–/– mice. Original magnification ×400. (c) Collagen expression in kidneys from 5 day–obstructed and sham-operated kallikrein transgenic and control (Sprague Dawley) rats. One group was treated with HOE-140. n = 5 per group. *P < 0.05 compared with sham-operated rats; ^‡P < 0.05 compared with UUO kallikrein transgenic rats without HOE-140. (d) Collagen expression in kidneys from 5 day–obstructed B2^+/+ mice treated with saline only or with saline containing HOE-140 at 500 μg/kg/d; n = 10 per group. Data expressed as the mean ± SD percentage of the interstitial area stained; *P < 0.05 compared to without HOE-140.