Basal, but not overload-induced, myonuclear addition is attenuated by NG-nitro-L-arginine methyl ester (L-NAME) administration.
The purpose of this study was to examine the effect of blocking nitric oxide synthase (NOS) activity via NG-nitro-L-arginine methyl ester (L-NAME) on myonuclear addition in skeletal muscle under basal and overloaded conditions. Female Sprague-Dawley rats (approx. 220 g) were placed into 1 of the following 4 groups (n = 7-9/group): 7-day skeletal muscle overload (O), sham operation (S), skeletal muscle overload with L-NAME treatment (OLN), and sham operation with L-NAME treatment (SLN). Plantaris muscles were overloaded via bilateral surgical ablation of the gastrocnemius muscles and L-NAME (0.75 mg/mL) was administered in the animals' daily drinking water starting 2 days prior to surgery and continued until sacrifice. Myonuclear addition was assessed as subsarcolemmal incorporation of nuclei labeled with 5-bromo-2'-deoxyuridine (approx. 25 mg.(kg body mass)-1.day-1) delivered via osmotic pump during the overload period. As expected, muscle wet mass, total protein content, fiber cross-sectional area, and myonuclear addition were significantly higher (p <or= 0.05) in O vs. S; however, only the increase in wet mass and total protein content (per body mass) were attenuated by L-NAME administration. Interestingly, L-NAME significantly reduced myonuclear addition by 75% in non overloaded muscles (SLN vs. S). Muscle hepatocyte growth factor protein content increased with overload, but was unaffected by L-NAME in either loading state. These data indicate that NOS inhibition in rat plantaris muscle attenuates myonuclear addition under basal, but not overloaded, conditions.
Gordon
Scott E
SE
Human Performance Laboratory, Department of Exercise and Sport Science, East Carolina University, Greenville, NC 27858, USA. gordonsc@ecu.edu
Westerkamp
Christopher M
CM
Savage
Kathleen J
KJ
Hickner
Robert C
RC
George
Sarah C
SC
Fick
Christopher A
CA
McCormick
Kathleen M
KM
D000284:Administration, Oral; D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects* / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D004326:Drinking; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D017228:Hepatocyte Growth Factor / Q000378:metabolism; D007150:Immunohistochemistry; D045586:Intranuclear Inclusion Bodies / Q000187:drug effects / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D012508:Sarcolemma / Q000187:drug effects / Q000378:metabolism; D032496:Satellite Cells, Skeletal Muscle / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D013997:Time Factors