Carly Schram with Dr. Dan Fitzsimons and Dr. Stacey Brickson

UW-Madison Medical School, Department of Physiology

The goal of this study was to determine the relative concentrations in the rat myocardium of beta myosin heavy chain (MHC) in the right ventricle and the epicardial and endocardial regions of the left ventricle. Myosin is a structural protein composed of two heavy chains and four light chains that work with actin filaments to provide the mechanism for movement by utilizing energy from ATP. The beta MHC isoform is known to be more efficient than the alpha MHC isoform, as far as work output compared to ATP cost. The heart must maintain a supply to demand balance of ATP, resulting in regional differences in the concentration of beta MHC in response to individual stresses. Gel electrophoresis and western blotting were used to measure the concentrations of beta MHC and alpha-actinin using commercially available antibodies. Densitometry was used to normalize beta MHC concentrations against alpha-actinin. The average relative concentrations were then compared between the regions, resulting in a fairly strong trend. The lowest concentration of beta MHC was in the right ventricle, then the epicardial left ventricle, with the highest concentration in the endocardial left ventricle. These results suggest that further research should be done using the mechanical measurements of force and power to more accurately quantify the relative concentrations and show the functional effects of these regional differences.