Ageing, but not yet senescent, rats exhibit reduced muscle quality and sarcoplasmic reticulum function.
OBJECTIVE
Reduced muscle force greater than expected from loss of muscle mass has been reported in ageing muscles. Impaired sarcoplasmic reticulum (SR) Ca(2+) release has been implicated as a possible mechanism, and attributed to several factors, including loss of ryanodine receptor (RYR) expression and protein binding. The aim of this study was to evaluate muscle quality and SR Ca(2+) release in ageing rats that were not so old that major atrophy had occurred.


METHODS
We collected in situ force data from the plantarflexor muscle group and muscle mass from the constituent muscles to determine muscle quality (force/mass) in adult (6-8 months) and ageing (24 months) rats (n=8/group). We evaluated SR Ca(2+) uptake and release, and determined expression of key proteins associated with Ca(2+) release [RYR and FK506 binding protein (FKBP)] and uptake (SERCA, parvalbumin, calsequestrin).


RESULTS
Plantarflexor force and muscle quality were reduced with ageing (approx. 28 and 34%, respectively), but atrophy was limited, and significant only in the medial gastrocnemius (approx. 15%). The fast phase of SR Ca(2+) release was reduced with ageing in both gastrocnemii, as was FKBP expression and FKBP-RYR binding, but RYR expression was not affected. Similar, but non-significant changes were present in the plantaris, but the soleus muscle generally showed no ageing-related changes.


CONCLUSIONS
These data suggest a possible role for impaired SR Ca(2+) release in ageing-related loss of muscle quality, although not through loss of RYR expression.
Russ
D W
DW
Laboratory for Integrative Muscle Biology, School of Physical Therapy, Ohio University, Athens, OH 45701, USA. russd@ohio.edu
Grandy
J S
JS
Toma
K
K
Ward
C W
CW
D000375:Aging / Q000502:physiology*; D000818:Animals; D020013:Calcium Signaling / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D051381:Rats; D011916:Rats, Inbred F344; D019837:Ryanodine Receptor Calcium Release Channel / Q000502:physiology*; D012519:Sarcoplasmic Reticulum / Q000502:physiology*
D019837:Ryanodine Receptor Calcium Release Channel