Microvasculature of Transgenic Mouse Hearts Lacking Actin Capping Protein

Transgenic mice bred to be deficient in actin capping protein have inefficient, abnormally formed muscle groups. The hearts of these transgenic mice are a potential model for the study of heart disease in humans. Because the structure of the cardiac muscle groups in transgenic mice is fundamentally different from normal mice, the structure of the microvasculature supplying those muscle groups may also be measurably different. In order to measure this difference in structure, casts were made of the coronary microvasculature in both transgenic and wild type mice (normal/control). After Forane (Isoflurane) anesthesia the heart was then exposed and a catheter was placed into the apex extending 1 mm into the left ventricle. A saline-heparin mixture (0.1 mL heparin to 10 mL 0.9% saline) of 60 mL was infused at a flow rate of 0.1 mL per minute. The infusion was continued with a Mercox casting polymer. After roughly 20 minutes infusion was stopped and the Mercox was allowed to polymerize; forming a solid cast of the coronary microvasculature. The hearts were placed in deionized water for 24 hours and then placed in a 15% weight by volume potassium hydroxide solution to digest the tissues away from the vascular cast. Upon completion of digestion the casts were freeze dried to preserve their structure and then analyzed using scanning electron microscopy. The procedure has been modified from the previous year in which polyurethane resin was used. Using Mercox resin in place of polyurethane has greatly improved the results of our experiment