| Skeletal muscle fibres typically undergo modifications in their mitochondrial content, concomitant with alterations in oxidative metabolism that occur during the development of the muscle fibre and in response to physiological stimulus. I examined how cold acclimation, a known physiological stimuli, affected the mitochondrial properties of two fish skeletal muscle fibre types and how the regulators of mitochondrial content differed between tissues. A two month acclimation period to 4;In addition, mtDNA copy number and steady state RNA levels were compared between tissues to discern if similar inter-tissue differences exist as reported for enzyme activities. Citrate synthase, a marker enzyme of mitochondrial content, differs by at least 10-fold on a per 9 tissue basis between red and white muscle. However, mtDNA copy number per g tissue, distinguished only a four-fold difference. Moreover, mtRNA varied in direct proportion to the relative amount of mtDNA. Conversely, the abundance of ANT1 mRNA was similar between red and white muscles. Thus, the determination of distinct mitochondrial profiles between tissues, likely result from the regulation of nuclear-encoded genes. |
