| Method |
With a knowledge of the contribution to rat SMR of skeletal muscle (estimates range from 13 to 42% mean 30%) and liver (10-20% mean 15%), the contribution of proton leak in liver and skeletal muscle to rat SMR can be estimated to be, on average, 20% (30 X 0.52 + 15 x 0.26) [range 10 (13 X 0.52 + 10 x 0.26) to 27 (42 x 0.52 + 20 x 0.26)%]. If the same proportions of liver and skeletal muscle oxygen consumption were uncoupled in humans, then the proton leak in these tissues would make a smaller contribution to SMR (- 15%) due to the smaller contribution of skeletal muscle in humans. Proton leak is present in mitochondria isolated from brain and kidney and has similar activity to that found in isolated liver mitochondria. Thus a reasonable estimate of the overall contribution of proton leak to SMR is -20%. |