Figure 1: Paricalcitol reduces isoproterenol-induced myocardial fibrosis and inhibits transforming growth factor-beta 1 (TGF-β1) expression in rats. (a-c) Picrosirius red staining for collagen shows that isoproterenol increases collagen levels causing myocardial fibrosis. After treatment with paricalcitol, the collagen level is decreased, reducing myocardial fibrosis. The left ventricle tissue is seen with collagen fibers of yellowish-orange birefringence by polarizing microscopy. Images are quantified using the count and measure module of ImageJ. Sum areas of total pixels were automatically generated via the count and measure module for the above settings and used to calculate the percentage of total collagen and background for each tissue. (d and e) Isoproterenol induces TGF-β expression. After treatment with paricalcitol, TGF-β1 expression is decreased, reducing the inducer of myocardial fibrosis. Statistical values are presented as mean ± standard error of the mean; n = 9. *P < 0.05 compared to the control group, #P < 0.05 compared to the isoproterenol + paricalcitol (experimental) group.