Figure 1. Mechanical properties of adult cardiac myocytes isolated from GRMD dogs.
Membrane-intact adult cardiac myocytes were isolated by enzymatic digestion from the hearts of 2 untreated 1-year-old GRMD dogs. (A) Microcarbon fibers were attached to the isolated myocytes, allowing mechanical manipulations and tension measurements (photo). Passive tension tracings from membrane-intact cardiac myocytes extended to sarcomere lengths indicated below the tracing. mN, millinewton. (B) Summary passive extension-tension curves are shown for membrane-intact cardiac myocytes isolated from wild-type and GRMD dogs and mdx mice. (C) Summary of the maximal sarcomere length tolerated by the myocytes. *P < 0.05. (D) Solubilization of membranes by detergents permits direct assessment of myofilaments. In a solution of nominal calcium, passive extension of myofilaments from wild-type and GRMD myocytes revealed no differences (7–8 cells from 2 dogs for each genotype). (E) Assessment of myofilament calcium sensitivity in membrane-solubilized myocytes revealed no differences between GRMD and wild-type myocytes. Data are from 5–7 myocytes isolated from 2–3 animals. pCa, –log[Ca2+].