Tissue-specific expression of tight junction mRNA in the kidney of mice. CLDN4 (A) and CLDN16 (B) mRNA expression were analyzed by real-time PCR. The level of CLDN4, and CLDN16 mRNA of kidney in WT, CaBP-9 k KO, -28 k KO, and DKO animals was evaluated in normal or calcium deficiency diet or calcium/vitamin D-deficient. Every result was normalized relative to β-actin. The values represent means ± SD of three separate experiments. * indicates *P < 0.05 vs WT of each diet.