ACL MYOTOXIN FROM Agkistrodon contortrix laticinctus ON FAST AND SLOW SKELETAL MUSCLE FIBERS OF MICE:ANALYSIS OF INJURY AND MUSCLE RECOVERY

Mini-Symposium - Abstracts

16 ACL MYOTOXIN FROM Agkistrodon contortrix laticinctus ON FAST AND SLOW SKELETAL MUSCLE FIBERS OF MICE - ANALYSIS OF INJURY AND MUSCLE RECOVERY

C.C. MORINI , E.C.L. PEREIRA , H.S. SELISTRE DE ARAÚJO , C.L. OWNBY , T.F. SALVINI

Laboratory of Neurosciences, Department of Physiotherapy, Federal University of São Carlos, São Carlos, SP, Brazil, Department of Physiological Sciences, Federal University of São Carlos, São Carlos, SP, Brazil, Department of Physiological Sciences, Oklahoma State University, Stillwater, OK, USA.

To study the response of individual skeletal muscle fiber types to snake venom PLA2 myotoxins, we have tested the effect of ACLMT on soleus (slow-twitch) and gastrocnemius (fast-twitch) mouse muscles. It was also the purpose of this work to analyze the general aspects of muscle recovery and possible changes in the incidence of fiber types in different periods (3 h, 3 and 21 days) after ACLMT injection. All animals received 5 mg of ACLMT/kg into the subcutaneous lateral region of the right hind limb, near the Achilles tendon. The contralateral muscles did not receive any kind of treatment and were used as control. Frozen muscles were cut at medial region in Microtome Cryostat (10µm cross-sections) and alternate serial sections stained with 1% Toluidine Blue / 1% Borax and for acid phosphatase (AcPase, E. C. 3. 1. 3. 2), myofibrillar ATPase activity (m-ATPase, E. C. 3. 6. 1. 3) after alkali (alc-mATP, pH 10.3), or acid preincubation (ac-mATP, pH 4.3), succinate dehydrogenase (SDH, E. C. 1. 3. 99. 1) and acetilcholinesterase (AChE, E. C. 3. 1. 1. 7). Signs of muscle fiber injury were identified three hours after ACLMT injection in both superficial and deep regions of soleus and gastrocnemius muscles by presence of several stages of myonecrosis, hypercontracted myofibrils densely clumped, intracellular fragmentation, edema and clear areas among muscle fibers. Three days later, these muscles showed clusters of recovered muscle fibers in the same regions. Some regeneration clusters presented AChE activity. Twenty-one days after ACLMT injection, the muscle fibers of soleus and gastrocnemius presented only chronic signs of damage as split fibers and centralized nucleus. By m-ATPase reactions it was possible to identify that both muscle fiber types I and II were injured in both muscles by ACLMT. Significative increased number of fiber type IIC (17.37 ± 4.11 versus 1.0 ± 0.6; p=0.008, paired Student t-test) and decrease of type II (60.7 ± 8.8 versus 76.8 ± 10.1; p=0.01, paired Student t-test) the gastrocnemius, suggest muscle fiber type change from type II to type I through type IIC. The increased number of type IIC fibers in the gastrocnemius is an evidence of axonal remodelling. Presence of AChE activity in the regeneration clusters and also in the split fibers, 3 and 21 days after ACLMT injection, respectively, in both soleus and gastrocnemius is an evidence that injury by ACLMT produced axonal remodeling. Although ACLMT is known by its myotoxic activity, the results presented here showed that it can also be used as a model to induce axonal remodeling and muscle fiber type change in both fast and slow skeletal muscles of mice.

CORRESPONDENCE TO: Dra. Tania de Fátima Salvini - Departamento de Fisioterapia, UFSCar, Rodovia Washington Luiz , km 235, CEP 13565-905, São Carlos, SP, Brasil. email:[e-mail]

Publication Dates

• Publication in this collection
  08 Jan 1999
• Date of issue
  1997