FIGURE 3.

Evaluation of the in vivo effect of 4-PBA treatment on mutant uromodulin maturation and trafficking defect. A, on Western blot analysis, uromodulin abundance in urine, standardized on equal creatinine, of six mice per Umod mutant mouse line and treatment group were analyzed and compared with the UMOD abundance of a wild-type mouse of the placebo treatment group. Urinary uromodulin protein excretion was reduced in 4-PBA and placebo-treated Umod mutant mice compared with placebo-treated wild-type mice. Furthermore, the uromodulin excretion with urine was much more decreased in homozygous Umod^C93F mutant mice than in homozygous mutant mice of the Umod^A227T mutant mouse line. Compared with genotype-matched mice of the placebo control group, Umod mutant mice of both lines receiving 4-PBA for 2 months excreted similar amounts of UMOD protein with urine as placebo control mice. B, staining patterns of uromodulin in TALH cells were similar in placebo control mice and 4-PBA-treated mice of the same genotype group. TALH cells of wild-type mice exhibited a diffuse cytoplasmic uromodulin immunopositivity with enforcement of the luminal membrane. In contrast, TALH cells of Umod mutant mice of both lines displayed a strong paranuclear immunopositivity for UMOD irrespective of kind of treatment. The chromogen was DAB; nuclear staining was done with hemalum.