Cardiac tissue remodels in response to increases in hormones, specifically Angiotensin II. Angiotensin II stimulates the proliferation of cardiac fibroblasts, the cell type that produces the extracellular matrix surrounding the cardiac myocytes, the contractile cells of the heart. Recent studies suggest that cardiac fibroblasts may alter their function as well as their number during cardiac remodeling. Our aim in this project is to determine if cardiac fibroblasts exposed to Angiotensin II may become electrically coupled by increasing expression of connexin 43, a gap junctional protein. Cardiac fibroblasts of neonatal or adult Sprague-Dawley rats were isolated using the Worthington Neonatal cardiomyocyte isolation system. This method includes obtaining the hearts and incubating them with trypsin and collagense. Myocytes were discarded after fibroblasts were isolated and adhered to culture plates. Fibroblasts were used through no more than three passages. After treatment with Angiotensin II (1 micromolar concentration), control and treated cells were lysed and assessed for connexin 43 using Western blot techniques.