Passive Stress in Myofibrils from Cardiomyopathic Hamsters

Abstract

Dilated cardiomyopahty (DCM) is a frequent heart disease characterized by cardiac dilation and contractile dysfunction. The Bio TO-2 hamster is a genetic animal model of human DCM. The purpose of this research is to study the progression of DCM by comparing over time the passive mechanical properties of left ventricular wall myofibrils from TO-2 hamsters to those from F1B control hamsters. To date, we measured the passive stress-sarcomere length relations for two myofibrils each from experimental and control animals aged 36 weeks. Myofibrils were attached at one end to a glass needle controlled by a motor for stretching, and at the other end to a silicon-nitride nanolever of known stiffness for force measurements. Sarcomere lengths were measured from the myofibrillar striation patterns. Passive stresses in the experimental and control myofibrils were comparable. More passive mechanical experiments will be performed to confirm this result. In a single myofibril, titin is thought to be responsible for essentially all of the passive stress response to stretch (Linke et al., 1994; Bartoo et al., 1997). Titin depletion experiments and titin molecular weight determination will therefore also be performed to detect changes in titin isoform.View Large Image | View Hi-Res Image | Download PowerPoint Slide