Involvement of nitric oxide synthase in skeletal muscle adaptation to chronic overload.
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; approximately 100 mg x kg-1 x day-1) in drinking water. Thirty-eight female Sprague-Dawley rats (approximately 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 approximately 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.
Smith
Lori W
LW
Department of Kinesiology, Texas Woman's University, Denton 76201, USA.
Smith
John D
JD
Criswell
David S
DS
D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001835:Body Weight; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006614:Hindlimb; D006984:Hypertrophy / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000032:analysis / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020033:Protein Isoforms / Q000032:analysis / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D004791:Enzyme Inhibitors; D020033:Protein Isoforms; D019001:Nitric Oxide Synthase; D018995:Myosin Heavy Chains; D019331:NG-Nitroarginine Methyl Ester