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First published online September 14, 2007
Journal of Experimental Biology 210, 3356-3360 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.007088
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Chronic electrical stimulation drives mitochondrial biogenesis in skeletal muscle of a lizard, Varanus exanthematicus

Paul J. Schaeffer1,*, Scott D. Nichols2 and Stan L. Lindstedt2,3

1 Department of Zoology, Miami University, Oxford, OH 45056, USA
2 Department of Biological Sciences, Northern Arizona University Flagstaff, AZ, USA
3 Department of Physiology, University of Arizona School of Medicine, Tucson, AZ, USA

* Author for correspondence (e-mail: schaefpj{at}muohio.edu)

Accepted 29 May 2007

We investigated the capacity for phenotypic plasticity of skeletal muscle from Varanus exanthematicus, the savannah monitor lizard. Iliofibularis muscle from one leg of each lizard was electrically stimulated for 8 weeks. Both stimulated and contralateral control muscles were collected and processed for electron microscopy. We used stereological analysis of muscle cross-sections to quantify the volume densities of contractile elements, sarcoplasmic reticulum, mitochondria and intracellular lipids. We found that mitochondrial volume density was approximately fourfold higher in the stimulated muscle compared to controls, which were similar to previously reported values. Sarcoplasmic reticulum volume density was reduced by an amount similar to the increase in mitochondrial volume density while the volume density of contractile elements remained unchanged. Intracellular lipid accumulation was visibly apparent in many stimulated muscle sections but the volume density of lipids did not reach a significant difference. Although monitor lizards lack the highly developed aerobic metabolism of mammals, they appear to possess the capacity for muscle plasticity.

Key words: muscle plasticity, sarcoplasmic reticulum, intracellular lipid, exercise, activity






© The Company of Biologists Ltd 2007