Electrical stimulation of leg muscles increases tibial trabecular
bone formation in unloaded rats.
Zerath, Erik, Francis Canon, Charles-Yannick Guezennec, Xavier Holy,
Sylvie Renault, Catherine Andr[acute]e.
D[acute]epartement de Physiologie Analytique, Centre
d'[acute]etudes et de Recherches en M[acute]edecine
A[acute]erospatiale, Centre d'Essais en Vol, 91220 - Br[acute]etigny
-sur-Orge, France
APStracts 2:0319A, 1995.
Rat head-down hindlimb suspension (HS) has been shown to induce
hindlimb cancellous bone loss. As HS is known to associate unloading
with progressive disappearance of hindlimb muscle contractions, we
investigated whether persisting muscle motion could modify suspension
induced bone disorders, or even prevent them. Chronic electrical
stimulation (ES) was applied to leg muscles of rats during three-week
hindlimb suspension, the lack of support for hindlimbs maintaining a
hypodynamic situation. The histomorphometric characteristics of the
proximal tibial metaphysis were analyzed. At the end of this protocol
of combined suspension and stimulation, trabecular bone loss remained
similar to that of non stimulated HS animals. However, trabecular
bone cell activity parameters showed greater bone formation after
muscle stimulation in unloaded animals, with significantly increased
ostoblastic, osteoid and mineralizing surfaces. In addition,
periosteal mineral apposition rate and cancellous bone formation
rate, markedly decreased by suspension, were not significantly
different in suspended stimulated compared with normal loaded
animals. This enhanced formation activity could be related to
persistence of muscle activity, as shown by partial preservation of
muscle mass. But direct electrical effects on bone cannot be
excluded. Thus, in spite of muscle stimulation, with enhanced bone
formation, isolated suppression of hypokinesia has not been able to
counteract bone effects of unloading. This supports the hypothesis of
the importance of mechanical loading to maintain bone architecture.
Received 16 September 1994; accepted in final form 13 July 1995.
APS Manuscript Number A973-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.