Role of myoglobin in regulating respiration during muscle contraction

Abstract

Oxygen (O 2) transport from air to mitochondria depends on both the mechanisms of convection and diffusion. In the final step of the O 2 cascade, from the capillary to myocyte, O 2 is transported into cells via diffusion according to the potential differences in PO 2 across plasma membranes. Myoglobin (Mb), an important cellular O 2 binding protein that is expressed in skeletal and cardiac muscle cells, has been known as an O 2 store or O 2 transporter for more than half a century. However during the last decade, Mb functions have been reassessed as a result of further knowledge gained from Mb-deficient mice that suggest other functions beyond its function as an O 2 store. At first glance, Mb-deficient mice do not show any superficial physiological deficits. However, homeostatic mechanisms, including increased capillary density that tends to steepen the PO 2 gradient to the mitochondria, effectively shorten the diffusion path for O 2. Recent research demonstrated that Mb is releasing its binding O 2 at onset of muscle contraction to manipulate intracellular O 2 content. The O 2 gradient Mb substantially contributes to nitric oxide homeostasis, and could interact with substrates such as fatty acid. This recent experimental evidence will help us to refine our understanding of Mb physiological function and establish a basis for further research.

Heat-induced endoplasmic reticulum stress in soleus and gastrocnemius muscles and differential response to UPR pathway in rats

“…SL muscle being an oxidative muscle has a greater proportion of myoglobin than GS muscle. Myoglobin acts as an oxygen store and facilitates oxygen diffusion in muscle cells at the onset of muscle contraction (Masuda et al 2013). Disruption of skeletal muscle membrane integrity decreases the myoglobin levels and thus, oxygen availability to contracting muscles.…”

Noninvasive optical imaging of resistance training adaptations in human muscle

“…While significant increases in THbMb and HbMbO2 were seen with training, it is unclear whether these changes come from increased myoglobin content, increased perfusion to formerly closed capillaries before training, increased capillary density, or other modifications throughout the complex skeletal muscle environment. The literature is equivocal on whether myoglobin concentrations in human muscle change with RT 37 . Another possibility is that resting blood flow into the gastrocnemius muscles increased and a portion of previously closed capillaries were perfused.…”

FNIP-1 Expression in Mice Muscle Negatively Correlated with Myoglobin Level and Endurance Performance on Treadmill Run Test

“…It was proposed to be excluded from the Myh7b/ miR-499 action on FNIP-1 expression. On the contrary, myoglobin was the main characteristic found in type-1 slow oxidative myocytes which more in mitochondria number and oxidative enzymes level (Masuda et al, 2013;Nemeth & Lowry, 1991). It was still uncertain whether myoglobin level correlated with FNIP-1 expression or not.…”