Cardiac, Skeletal, and smooth muscle mitochondrial respiration: Are all mitochondria created equal?
Research output: Contribution to journal › Journal article › Research › peer-review
Unlike cardiac and skeletal muscle, little is known about vascular smooth muscle mitochondrial function. Therefore, this study examined mitochondrial respiratory rates in the smooth muscle of healthy human feed arteries and compared with that of healthy cardiac and skeletal muscle. Cardiac, skeletal, and smooth muscle was harvested from a total of 22 subjects (53±6 yrs) and mitochondrial respiration assessed in permeabilized fibers. Complex I+II, state 3 respiration, an index of oxidative phosphorylation capacity, fell progressively from cardiac, skeletal, to smooth muscle (54±1; 39±4; 15±1 pmol•s(-1)•mg (-1), p<0.05, respectively). Citrate synthase (CS) activity, an index of mitochondrial density, also fell progressively from cardiac, skeletal, to smooth muscle (222±13; 115±2; 48±2 umol•g(-1)•min(-1), p<0.05, respectively). Thus, when respiration rates were normalized by CS (respiration per mitochondrial content), oxidative phosphorylation capacity was no longer different between the three muscle types. Interestingly, Complex I state 2 normalized for CS activity, an index of non-phosphorylating respiration per mitochondrial content, increased progressively from cardiac, skeletal, to smooth muscle, such that the respiratory control ratio (RCR), state 3/state 2 respiration, fell progressively from cardiac, skeletal, to smooth muscle (5.3±0.7; 3.2±0.4; 1.6±0.3, pmol•s(-1)•mg (-1) p<0.05, respectively). Thus, although oxidative phosphorylation capacity per mitochondrial content in cardiac, skeletal, and smooth muscle suggest all mitochondria are created equal, the contrasting RCR and non-phosphorylating respiration highlight the existence of intrinsic functional differences between these muscle mitochondria. This likely influences the efficiency of oxidative phosphorylation and could potentially ROS production.
|Journal||American Journal of Physiology: Heart and Circulatory Physiology|
|Number of pages||7|
|Publication status||Published - 6 Jun 2014|