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International journal of Morphology

versión On-line ISSN 0717-9502

Int. J. Morphol., 26(1):63-67, 2008.

Fiber form Composition in Semitendinous Muscle of Wistar Rats e Effects the Intermittent training on that Hypertrophy

Composición de los Tipos de fibra del muscular Semitendinoso de Ratas Wistar y los Efectos del Entrenamiento Intermitente en su Hipertrofia

*Alexandre ferreira & **Gerson eduardo Rocha campos

* Sport"s institute ­ faculdade Integradas arcebispo de Campinas - METROCAMP. Correção II, R. Madre maria Santa Margarida, s/n - nova Campinas, Campinas, eles são Paulo, Brasil. ** anatomia Department ­ biological Institute, Universidade estadual de Campinas ­ UNICAMP, Brasil.

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SUMMARY: Skeletal muscle respond to number of stimuli transforming their phenotype. Muscular fibers adaptation capability is related to a presence of several myosin heavy chains (MHC). These expressão four varieties of pure fibers: I, IIA, IID and IIB include MHCI, IIa, IId and IIb, respectively. Amongst pure fibers, there ~ ~ hybrid fibers, i m sorry can expressão two or much more types that myosins. In this study, varieties of fibers constituting masculine Wistar rats semitendinous e their myosin hefty chains, and also influence the intermittent cultivate on hypertrophy of this fibers have been checked with MATPase histochemical technique e electrophoretic protein separation. Todos types of pure e hybrid muscular fiber have actually been found, however ns fibers of the types IIA, IID e IIB were predominant, featuring muscle as naquela fast-contracting one. Training has actually promoted músculo fibers transition with a significant increase of fibers of IC, IIAD e IIDB type. A cross-section increase of yarn of IIDB e IIB kind has also been noticed. In summary, semitendinous muscle is essentially constituted by fast-contracting fibers and training could promote transition and hypertrophy that these rapid fibers.

KEY WORDS: Semitendinous muscle; Muscle fibers; Intermittent training; Hypertrophy.

RESUMEN: sobrenome músculos esqueleto- responden der diversos estímulo cambiando su fenotipo. La capacidad de adaptación de las fibra musculares está relacionada con la presencia de diversificado miosinas de cadena pesado (MHC). Esses miosinas expresan cuatro tipos de fibras puras: I, IIA, IID, IIB, eu imploro seu perdão contienen MHCI IIa IId IIb, respectivamente. Adentraram las fibra puras hay fibra híbridas, las cuales pueden expresar são de o más modelo de miosinas. En este trabajo, se observaron los tipos de fibra y las cadenas pesadas de miosinas del muscular semitendinoso en ratas Wistar macho, así como también, la influencia del entrenamiento intermitente en la hipertrofia de aquellas fibras, a través de la habilidade histoquímica de mATPasa y separación eletroforética de proteínas. Tudo los tipos de fibra musculares puro e híbridas fueron encontradas, siendo las fibra de tipo IIA IID y IIB predominantes, através ser un muscular de contracción rápida. El entrenamiento promovió la transición de las fibras musculares con un aumentar significativo de las fibras del modelo IC, IIAD y IIDB. En una sección transversal, un ascendente de fibras del modelo IIDB y IIB también fue reportada. En resumen, el muscular semitendinoso está compuesto esencialmente através fibras de contracción rápida y el entrenamiento puede promover la transición e hipertrofia de las fibras musculares rápidas.

PALABRAS CLAVE: músculo semitendinoso; fibras musculares; Entrenamiento intermitente; Hipertrofia.


The existence of various myosin heavy chains (MHC) allows skeletal muscles to adapt to numerous stimuli. These adaptations happen through gene changes that will certainly express a new músculo fiber pattern, contributing this caminho to naquela heterogeneous phenotype (Demirel et al., 1999).

In adult rat bones muscles, there ~ ~ four myosin heavy chains: MHCI, i m sorry will express slow-contracting the I form and, MHCIIa, MHCIId e MHCIIb, existing in fast-contracting yarn of IIA, IID e IIB types, dong (Campos et al., 2002). Hybrid fibers can be found among pure fibers, expressing two or more myosin types (Tajsharghi et al., 2004). This way, details stimuli used on muscles have the right to provoke change both from I to IIB (I=>IIA=>IID=>IIB) and from IIB to ns (IIB=>IID=>IIA=>I), constantly passing v hybrid ones, thus an altering their phenotype.

Physical practice is one of a specific determinants affecting muscular fiber change (Andersen et al., 2000; Pette & Staron, 2001). Para example, low-intensity e long- duration physical training might induce naquela conversion a partir de fast to sluggish fibers. On a other hand, a high-intensity and short-duration training can lead to an opposite transition, the is, são de slow to fast (Caiozzo et al., 2003).

the purpose the this pesquisar is to analysis fiber varieties constituting masculine Wistar rat semitendinous muscle and its myosin heavy chains, and also to concertos these músculo fiber actions when submitted to intermittent training.


Animals. Sixteen Wistar breed e 21-day old male rats were used in the study. Dois groups have been constituted com eight pets each, a control group (CG) e a trained group (TG). During ns experimentation, animals were maintained in der controlled-temperature environment (18 come 22C), with der photoperiod that 12 hours and provided com food e water advertisement libitum. Training protocol. Pets have been trained on a motorized treadmill, throughout 6 days/weeks, para 8 weeks with intermitent maintain protocol (Table I) (Smolka et al., 2000). CG animals have no performed any kind of kind the exercise.


Sample preparation. After ns training period, pets were sacrificed com an overdose the Ketamine e Kylasine Chloridrate (1:1). ~ this procedure, semitendinous muscle was removed e frozen in cooled isopentane in fluid nitrogen at ­176C and stored in der freezer at -80°C. Then, 12 mm special cross ar were obtained são de samples, in a cryostat, at 24C.

Histochemical and morphometric analysis. Sections have been submitted to mATPase (myofibrillar adenosine triphosphatase) reaction (Pette & Staron) ~ pre-incubations in pH the 4.3, 4.5 (Brooke & Kaiser, 1970) and 10.3 (Guth & Samaha, 1970), and fibers species were identified and counted. Cross-section area of about fifty fibers of each form (I-IIA-IID-IIB) per fauna e flora was measure up through photo ProExpress program.

Biochemical analysis. Part of every sample have actually been collected porque o biochemical analysis. These were placed in 0.5ml of adhering to medium: 10% (w/v) glycerol, 5% (v/v) 2 mercaptoethanol and 2.3% (w/v) salt dodecylsulfate (SDS), in 62.5 mM Tris/HCL buffer (pH 6,8). Cut were agitated during 1 minute e heated for 19 minutes, at 60C. Extract portions (7 ml) to be submitted to electrophoresis in gel (gradient the 7-10%) that polyacrylamine (SDS), with 17-18 hrs of to run at 120V. ~ coloration with silver (Blum et al., 1987), gel era used to determine presence the MHC identified according to respective molecular masses. Naquela soleum muscle sample was also consisted of as control, as it presents in rats around 95% the MHCI e 5% of MHCII (Staron et al., 1999).

Statistical analysis. Results have actually been analyzed e expressed through their averages e standard deviation. Statistical meaning of differences between averages of both groups was calculated through test t of Student e Mann Whitney ao independent samples, with Instat program. Significance for p RESULTS

Fibers types and Myosin hefty chains (MHC). Tudo de pure fiber varieties were current in this muscle (I, IIA, IID e IIB), as well as hybrid yarn IC, IIC, IIAD and IIDB (Fig. 1).


v electrophoretic separation, visibility of 4 myosin heavy chains (MHCI, IIa, IId e IIb) ser estar evidenced in both groups. The IIb foi ~ predominant, a IIa and IId have actually showed naquela slight difference as to migration distance, e a semelhante proportion, while band I era slightly i found it (Fig. 2).


maintain effects. A significant rise on hybrid yarn of IC, IIAD and IIDB species could be i found it (Fig. 3) when era analyzed the tudo de muscle. Cross-section area of vermelho portion fibers of semitendinous muscle gift no change (Table II.B). Top top white portion, apenas um IIB yarn showed a significant increase in their area (Table II.C) and, when both muscle sections were analyzed together, it foi ~ noticed that IIDB hybrid fibers experienced hypertrophy (Table II.A).


According to histochemical analysis of Wistar rat semitendinous muscle, tudo pure fibers were present, in which fast-contracting ones (IIA, IID e IIB) were ns most expressive in ns bouth groups, thus, semitendinous muscle deserve to be rated together an essentially fast-contracting muscle. Some studies carried o fim with ns same muscle, but from other animal species, proved results the corroborate this details (Delp & Duan, 1996; Jurie et al., 1998). Electrophoretic separation the myosins in semitendinous muscle samples evidenced four bands: IIb, uncovered in bigger quantity, complied with by IId, IIa e I, respectively. This way, encontro confirm existence and proportion the IIB, IID, IIA and I fibers checked out in optical microscopy (Figs.1 e 2).

Physical practice is one important fator for músculo phenotype conversion. It deserve to lead to der fiber bi-directional change (Goldispink, 2003), relying on its periodicity, which deserve to be set according to continuous charge principle (continuous training), mainly in long-duration activities, with higher volume e lower intensities. Or periodic charge one, whose directing principle is naquela lower duration e higher intensity, functions that deserve to be worked out in intermittent training, in which physical exercise is perform in der discontinuous manner and is interrupted at regular intervals and then, applied again.

This way, protocol applied in this pesquisar is considered as intermittent (Smolka et al.) and induced muscular fibers changes. Therefore, observing ns Fig. 3, an increase of IC, IIAD e IIDB hybrid fibers could be noticed, suggesting that training has actually induced MHC levels changes, through disturbances in genes expressing these proteins (Harrison et al., 2002), but era not may be to totally convert them, maybe because of protocol application equipe or to and intensity that foi ~ not sufficiently alto to promote complete conversion. Nevertheless, fast-contracting fibers group presented the higher interference. So, that applied protocol recruits much more fast-contracting fibers 보다 slow-contracting ones. Training used could not induce far-ranging changes on vermelho region músculo fibers size (Table IIB). ~ above white region, over there was naquela significant rise of yarn IIB area, and can be noticed on a whole muscle a hypertrophy of a IIDB (Table IIC and A), both representing fast-contracting group. De acordo com to vault studies, most recruited fibers in short-duration exercises ser estar fast-contracting ones, indicating a high proteins manufacturing of few of these fibers, provoking your hypertrophy (Bottinelli & Reggiani, 2000; Talmadge, 2000; Lin et. Al., 2002).

In summary, it era demonstrated that semitendinous muscle is mainly made up by fast-contracting fibers e that intervalled training can promote muscular fibers transition, with naquela significant rise of hybrid yarn IIC-IIAD- IIDB e a hypertrophy the fast-contracting yarn IIDB and IIB.

ACKNOWLEDGEMENTS. The CNPq ­ Brazil by a support come carry fora this work. To the anatomia and Biochemistry department of a Biology institute ­ UNICAMP, Brazil. REFERENCES

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