Involvement of nitric oxide synthase in skeletal muscle adaptation to chronic overload

• Published in: Journal of applied physiology (1985) Vol. 92; no. 5; pp. 2005 - 2011
• Main Authors: Smith, Lori W, Smith, John D, Criswell, David S
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.05.2002; American Physiological Society
• Subjects: Adaptation, Physiological - physiology; Animals; Biological and medical sciences; Body Weight; Dose-Response Relationship, Drug; Enzyme Activation - drug effects; Enzyme Inhibitors - pharmacology; Female; Fundamental and applied biological sciences. Psychology; Hindlimb; Hypertrophy - metabolism; Muscle Fibers, Skeletal - drug effects; Muscle Fibers, Skeletal - enzymology; Muscle Fibers, Skeletal - ultrastructure; Muscle, Skeletal - chemistry; Muscle, Skeletal - drug effects; Muscle, Skeletal - metabolism; Muscular system; Myosin Heavy Chains - analysis; Myosin Heavy Chains - metabolism; NG-Nitroarginine Methyl Ester - pharmacology; Nitric Oxide Synthase - antagonists & inhibitors; Nitric Oxide Synthase - metabolism; Nitrogen; Oxygen; Protein Isoforms - analysis; Protein Isoforms - metabolism; Rats; Rats, Sprague-Dawley; Space life sciences; Striated muscle. Tendons; Vertebrates: osteoarticular system, musculoskeletal system; Rat; Enzyme; Rodentia; Striated muscle; Nitric-oxide synthase; Biomechanics; Vertebrata; Compensatory hypertrophy; Mammalia; Overload; Nitric oxide; Oxidoreductases; Adaptation
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00950.2001

1  Department of Kinesiology, Texas Woman's University, Denton, Texas 76201; and 2  Center for Exercise Science, University of Florida, Gainesville, Florida 32611 The purpose of this study was to determine the necessity of nitric oxide (NO) for hypertrophy and fiber-type transition in overloaded (OL) skeletal muscle. Endogenous NO production was blocked by administering N G -nitro- L -arginine methyl ester ( L -NAME; 0.75 mg/ml; ~100 mg ·   kg 1 · day 1 ) in drinking water. Thirty-eight female Sprague-Dawley rats (~250 g) were randomly divided into four groups: control-nonoverloaded (Non-OL), control-OL, L -NAME-Non-OL, and L -NAME-OL. Chronic overload of the plantaris was induced bilaterally by surgical removal of the gastrocnemius and soleus. Rats in the Non-OL groups received sham surgeries. L -NAME treatment began 24 h before surgery and continued until the rats were killed 14 days postsurgery. Although OL induced hypertrophy in both control (+76%) and L -NAME (+39%) conditions ( P  < 0.05), mean plantaris-to-body mass ratio in the L -NAME-OL group was significantly lower ( P  < 0.05) than that in the control-OL group. Microphotometric analysis of histochemically determined fiber types revealed increases in cross-sectional area ( P  < 0.05) for all fiber types (types I, IIA, and IIB/X) in the OL plantaris from control rats, whereas L -NAME-OL rats exhibited increases only in type I and IIB/X fibers. SDS-PAGE analysis of myosin heavy chain (MHC) composition in the plantaris indicated a significant ( P  < 0.05) OL effect in the control rats. Specifically, the mean proportion of type I MHC increased 6% ( P  < 0.05), whereas the proportion of type IIb MHC decreased ~9% ( P  < 0.05). No significant OL effects on MHC profile were observed in the L -NAME rats. These data support a role of NO in overload-induced skeletal muscle hypertrophy and fiber-type transition. rat; plantaris; compensatory hypertrophy; N G -nitro- L -arginine methyl ester; fiber type