Details

Autor(en) / Beteiligte

• Geiger, Paige C
• Cody, Mark J
• Macken, Rebecca L
• Sieck, Gary C

Titel

Maximum specific force depends on myosin heavy chain content in rat diaphragm muscle fibers

Ist Teil von

• Journal of applied physiology (1985), 2000-08, Vol.89 (2), p.695-703

Ort / Verlag

Bethesda, MD: Am Physiological Soc

Erscheinungsjahr

2000

Quelle

MEDLINE

Beschreibungen/Notizen

• Departments of Anesthesiology and of Physiology and Biophysics, Mayo Clinic and Foundation, Rochester, Minnesota 55905 In the present study, myosin heavy chain (MHC) content per half sarcomere, an estimate of the number of cross bridges available for force generation, was determined in rat diaphragm muscle (Dia m ) fibers expressing different MHC isoforms. We hypothesize that fiber-type differences in maximum specific force [force per cross-sectional area (CSA)] reflect the number of cross bridges present per CSA. Studies were performed on single, Triton X-100-permeabilized rat Dia m fibers. Maximum specific force was determined by activation of single Dia m fibers in the presence of a high-calcium solution (pCa, log Ca 2+ concentration of 4.0). SDS-PAGE and Western blot analyses were used to determine MHC isoform composition and MHC content per half sarcomere. Differences in maximum specific force across fast MHC isoforms were eliminated when controlled for half-sarcomere MHC content. However, the force produced by slow fibers remained below that of fast fibers when normalized for the number of cross bridges available. On the basis of these results, the lower force produced by slow fibers may be due to less force per cross bridge compared with fast fibers. skinned fibers; force per cross bridge; fiber morphometry