Effects of nitric oxide on the contraction of skeletal muscle

Area of Science:

• Muscle physiology
• Biochemistry
• Cell signaling

Background:

• Nitric oxide (NO) plays a crucial role in regulating various physiological processes, including skeletal muscle function.
• The dual role of NO in skeletal muscle, acting both directly and indirectly, requires detailed elucidation.
• Understanding NO's impact is vital for comprehending muscle adaptation and performance.

Purpose of the Study:

• To review and classify the effects of nitric oxide (NO) on skeletal muscle fibers.
• To differentiate between direct NO effects and those mediated by cyclic guanosine monophosphate (cGMP).
• To elucidate the functional consequences of NO signaling on muscle contraction and metabolism.

Main Methods:

• Literature review of studies investigating nitric oxide's effects on skeletal muscle.
• Analysis of direct effects of NO on proteins (nitrosation, nitrosylation).
• Analysis of indirect effects mediated by cGMP signaling pathways.

Main Results:

• Direct NO effects: Depression of force, shortening velocity, glycolysis, and mitochondrial respiration; variable effects on calcium release channels, generally 'braking' contraction and metabolism.
• cGMP-mediated NO effects: Increased shortening velocity, mechanical power, force development rate, glucose uptake, and mitochondrial respiration; decreased relaxation time; 'slow-to-fast' muscle shift.
• Negligible impact on maximal isometric force for both direct and indirect pathways.

Conclusions:

• Nitric oxide exerts distinct effects on skeletal muscle fibers through direct and cGMP-mediated pathways.
• Direct NO actions tend to inhibit muscle contraction and metabolism.
• cGMP-mediated NO signaling enhances muscle power and metabolic efficiency, inducing a 'slow-to-fast' fiber type transformation.