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  • Title: Basal, but not overload-induced, myonuclear addition is attenuated by NG-nitro-L-arginine methyl ester (L-NAME) administration.
    Author: Gordon SE, Westerkamp CM, Savage KJ, Hickner RC, George SC, Fick CA, McCormick KM.
    Journal: Can J Physiol Pharmacol; 2007 Jun; 85(6):646-51. PubMed ID: 17823627.
    Abstract:
    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.
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