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Properties of extensor digitorum longus muscle and skinned fibers from adult and aged male and female Actn3 knockout mice
Author(s) -
Chan Stephen,
Seto Jane T.,
Houweling Peter J.,
Yang Nan,
North Kathryn N.,
Head Stewart I.
Publication year - 2011
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.21778
Subject(s) - endocrinology , extensor digitorum longus muscle , medicine , extensor digitorum muscle , endoplasmic reticulum , caffeine , knockout mouse , chemistry , anatomy , biology , skeletal muscle , soleus muscle , biochemistry , receptor
Absence of α‐actinin‐3, encoded by the ACTN3 “speed gene,” is associated with poorer sprinting performance in athletes and a slowing of relaxation in fast‐twitch muscles of Actn3 knockout (KO) mice. Our first aim was to investigate, at the individual‐fiber level, possible mechanisms for this slowed relaxation. Our second aim was to characterize the contractile properties of whole extensor digitorum longus (EDL) muscles from KO mice by age and gender. We examined caffeine‐induced Ca 2+ release in mechanically skinned EDL fibers from KO mice, and measured isolated whole EDL contractile properties. The sarcoplasmic reticulum of KO muscle fibers loaded Ca 2+ more slowly than that of wild‐types (WTs). Whole KO EDL muscles had longer twitch and tetanus relaxation times than WTs, and reduced mass and cross‐sectional area. These effects occurred in both male and female mice, but they diminished with age. These changes in KO muscles and fibers help to explain the effects of α‐actinin‐3 deficiency observed in athletes. Muscle Nerve, 2011