Treatment with exogenous BNP further reduces the pro-fibrotic effects of TGFβ on mechanically stretched fibroblasts. Human primary cardiac fibroblast cells underwent either biaxial mechanical stretch for 72 h or were left un-stretched (control). During this time, cells were either exposed to 10 ng/mL transforming growth factor beta (TGFβ) or 1,000 nM recombinant b-type natriuretic peptide (BNP), or both. Changes in alpha-smooth muscle actin (ASMA) protein expression were measured using western blotting and quantified using densitometry. Anti-tubulin was utilized as a loading control for western blotting. Bar graphs represent mean fold change ± SD. ***P < 0.001.