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Figure 4 Induction of expression of markers of hypertrophy and fibrosis and histologic phenotypes. (A) Relative expression levels of marker of hypertrophy (cardiac load) and fibrosis. The upper panels show relative expression levels of A-type natriuretic peptide (NPPA), B-type natriuretic peptide (NPPB), and sarcoplasmic reticulum calcium ATPase 2a (SERCA2a or ATP2A2) in the heart in the experimental groups, determined by real-time quantitative RT-PCR. All values were corrected for levels of mRNA in the NTG control group. Labels are as follows: 1: non-transgenic littermates (NTG); 2: target transgene only (TATA-cTnT-Q92); 3: regulator transgene only (GLp65); 4: bigenic in the placebo group; 5: bigenic mice on mifepristone group (16 days); and 6: bigenic mice off mifepristone for 16 days. All p values were <0.05 for comparisons of NPPA and NPPA levels between bigenic mice on mifepristone versus each of the other groups (t test) and among all groups (ANOVA). The lower panels show relative expression levels of cardiac collagens, namely COL1A1, COL1A1, and COL3A1 in the experimental groups. Labels are as above. All p values are <0.001 and <0.01 in comparing COL1A1 and COL3A1 levels, respectively, between bigenic mice on mifepristone versus each of the other groups (t test) and among all groups (ANOVA). (B) Histologic phenotypes in the NTG and bigenic mice in the placebo and mifepristone groups. The upper panels represent Sirius Red staining of thin myocardial sections used to determine CVF. The values under each micrograph indicate mean ± SD of CVF in the corresponding group. The lower panels show immunofluorescence micrographs stained with anti-laminin B monoclonal antibody and a rhodamine-conjugate secondary antibody to delineate the myocyte boundaries. Values under each panel indicate mean ± SD pixels per myocyte in each group.