Tolcapone reduced the relative kidney weight, plasma creatinine, plasma urea and albumin excretion. Shown are the effects of 3 months tolcapone treatment in PKD/Mhm and PKD/US males and females on (A) relative kidney weight (B) plasma creatinine, (C) plasma urea and (D) albumin excretion (mean ± SD). P values <0.001 are denoted by ***, between 0.001 < P < 0.01 by **, and P values between 0.01 < P < 0.05 by *.