Fig. 5. Phospho-SMAD1 expression is increased in the P10 TgALK3^QD/QD kidney. (A) Phospho-SMAD1 expression in TgALK3^QD/QD kidney. Left: Hematoxylin-stained control kidney tissue (medulla) stained with anti-phospho-SMAD1 antibody demonstrates very weak expression of phospho-SMAD1. Middle: Hematoxylin-stained tissue from a TgALK3^QD/QD mouse demonstrating a marked increase in phospho-SMAD1 expression. Right: Hematoxylin-stained tissue containing an epithelial cyst showing phospho-SMAD1 expression in cells lining the cyst. (B) Quantification of SMAD1 and phospho-SMAD1 protein expression in whole kidney lysate. Left: expression of total SMAD1 (unphosphorylated and phosphorylated) is similar in kidneys from control (white), TgALK3^QD (QD; gray) and TgALK3^QD/QD (QD/QD, black) mice. Right: phospho-SMAD1 expression is increased by 51% in TgALK3^QD versus control kidney, and by 86% in TgALK3^QD/QD kidneys. Representative blots are shown above. Data are mean±s.d. from four separate experiments.