Measuring Mechanical Properties, Including Isotonic Fatigue, of Fast and Slow MLC/mIgf-1 Transgenic Skeletal Muscle

  • Zaccaria Del Prete
  • Antonio Musarò
  • Emanuele Rizzuto
Article

Abstract

Contractile properties of fast-twitch (EDL) and slow-twitch (soleus) skeletal muscles were measured in MLC/mIgf-1 transgenic and wild-type mice. MLC/mIgf-1 mice express the local factor mIgf-1 under the transcriptional control of MLC promoter, selectively activated in fast-twitch muscle fibers. Isolated muscles were studied in vitro in both isometric and isotonic conditions. We used a rapid “ad hoc” testing protocol that measured, in a single procedure, contraction time, tetanic force, Hill’s (Fv) curve, power curve and isotonic muscle fatigue. Transgenic soleus muscles did not differ from wild-type with regard to any measured variable. In contrast, transgenic EDL muscles displayed a hypertrophic phenotype, with a mass increase of 29.2% compared to wild-type. Absolute tetanic force increased by 21.5% and absolute maximum power by 34.1%. However, when normalized to muscle cross-sectional area and mass, specific force and normalized power were the same in transgenic and wild-type EDL muscles, revealing that mIgf-1 expression induces a functional hypertrophy without altering fibrotic tissue accumulation. Isotonic fatigue behavior did not differ between transgenic and wild-type muscles, suggesting that the ability of mIgf-1 transgenic muscle to generate a considerable higher absolute power did not affect its resistance to fatigue.

Keywords

Transgenic muscle Twitch force Isometric and isotonic force Hill’s equation Muscle power measurement Muscle isotonic fatigue measurement 

Copyright information

© Biomedical Engineering Society 2008

Authors and Affiliations

  • Zaccaria Del Prete
    • 1
  • Antonio Musarò
    • 2
  • Emanuele Rizzuto
    • 2
  1. 1.Department of Mechanical and Aeronautical EngineeringUniversity of Rome “La Sapienza”RomeItaly
  2. 2.Department of Histology and Medical Embryology, IIMUniversity of Rome “La Sapienza”RomeItaly

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