E-C coupling and contractile characteristics of mechanically skinned single fibres from young rats during rapid growth and maturation

Abstract

The postnatal growth of rats involves a developmental phase (0 to ∼3 weeks), a rapid growth phase (∼3 to ∼10 weeks), and a slower maturation phase (∼10 weeks+). In this study, we investigated the age-related changes in excitation-contraction (E-C) coupling characteristics of mammalian skeletal muscle, during rapid growth (4-10 weeks) and maturation (10-21 weeks) phases, using single, mechanically skinned fibres from rat extensor digitorum longus (EDL) muscle. Fibres from rats aged 4 and 8 weeks produced lower maximum T-system depolarization-induced force responses and fewer T-system depolarization-induced force responses to 75% run-down than those produced by fibres from rats aged 10 weeks a..