Effects of altitude on myoglobin and mitochondrial protein in canine skeletal muscle.

Myoglobin and mitochondrial protein contents were measured spectrophotometrically in the sternothyroid muscle of 8 dogs, first in Dnver, at a PB of 635 mm Hg, and after a 3-week exposure to a PB of 435 mm Hg, using a hypobaric chamber. The PaO2 at a PB of 635 mm Hg was 81.9 mm Hg and at a PB of 435 mm Hg, it was 54.6 mm Hg. Myoglobin concentration increased from 3.67 +/- 1.07 to 5.47 +/- 0.90 mg/g fresh muscle while mitochondrial protein content increased from 3.04 +/- 0.80 to 4.96 +/- 2.59 mg N2/g fresh muscle upon exposure to simulated altitude. It is believed that these changes in the biochemistry of the muscle are related to alterations in muscle fiber type composition, which seem to be adaptive in nature.