title: Role of nitric oxide in muscle regeneration following eccentric muscle contractions in rat skeletal muscle.
abstract: We examined the role of nitric oxide (NO) in muscle repair and regeneration following repetitive eccentric contractions (ECC). A standardized exercise protocol was used to create eccentric contraction-induced injury to the left tibialis anterior muscle of 48 male Wistar rats (body wt 250-350 g), using a customized isokinetic test device and a bout of 40 ECCs under electrical stimulation. A nitric oxide synthase inhibitor, N(G)-nitro-L-arginine-methyl ester (L-NAME; 35 mg kg(-1) day(-1)), was included in the diet for half the animals (n = 24) beginning 3 days prior to the ECC and continuing throughout the experiment, whereas the other half (n = 24) received a control diet. ECC/+L-NAME and ECC/-L-NAME were killed after the ECC protocol at 0, 1, 3 and 7 days (n = 6 on each day). An unexercised contralateral limb with and without L-NAME infusion served as a respective control muscle at each time point. Muscle NO content, skeletal muscle damage, leukocyte infiltration, calpain activity, and MyoD and myogenin expression were assessed. NO has both pro-inflammatory and anti-inflammatory properties, and several possible roles for NO in skeletal muscle damage have been postulated. NO content was greater in the ECC/-L-NAME group at all time points (p < 0.05) compared to ECC/+L-NAME. Additionally, significant differences in NO content were observed on day 0 (p < 0.05), and day 3 (p < 0.05), ECC/+L-NAME versus ECC/-L-NAME. One day following the bout of ECC, and NO levels were increased in the ECC/-L-NAME group. Three days following ECC, there was greater myofiber damage (measured by β-glucuronidase activity) and leukocyte invasion in the ECC/-L-NAME group as compared to the ECC/+L-NAME group. One day after ECC, calpain activity was significantly increased in ECC/-L-NAME compared with control muscles (p < 0.05). On days 3 and 7, Myo-D and myogenin gene expression was increased in both groups; however, the degree of regeneration was less in the ECC/+L-NAME-treated animals. These data suggest that NO dynamics have important implications in the regulation of various factors during skeletal muscle regeneration following damaging eccentric muscle contractions.
authors.affiliation: Faculty of Bio-Industry, Tokyo University of Agriculture, 196 Yasaka, Abashiri, Hokkaido, 099-2493, Japan. t3sakura@bioindustry.nodai.ac.jp
authors.forename: Tomonobu
authors.initials: T
authors.lastname: Sakurai
authors.forename: Osamu
authors.initials: O
authors.lastname: Kashimura
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kano
authors.forename: Hideki
authors.initials: H
authors.lastname: Ohno
authors.forename: Li Li
authors.initials: LL
authors.lastname: Ji
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Izawa
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Best
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D005966:Glucuronidase / Q000096:biosynthesis; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010805:Physical Conditioning, Animal; D051381:Rats; D017208:Rats, Wistar; D012038:Regeneration / Q000187:drug effects*
chemical_list: D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D005966:Glucuronidase; D019331:NG-Nitroarginine Methyl Ester