Expression of myogenic regulatory factor MyoD in skeletal muscle of pacu (Piaractus mesopotamicus) during growth / Expressão do fator de regulação miogenica MyoD, na musculatura estriada esqueletica do pacu (Piaractus mesopotamicus), durante o crescimento

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Skeletal muscle growth in fish occurs by hypertrophy and hyperplasia and is dependent of the proliferation and differentiation of myogenic progenitor cells, events regulated by the diferential expression of the myogenic regulatory factors (MRFs). The aim of this study was to analyze the hyperplasia and hypertrophy processes and the MRF MyoD expression in the white muscle in pacu (Piaractus mesopotamicus) during growth. Juvenile (n=5) and adult (n=5) fishes were anaesthetized, sacrificed and the weight (g) and the total length (cm) were determined. White muscle samples from dorsal region of each sample, in each growth phase, were collected and and immersed in n- Hexane cooled in liquid nitrogen. Transverse sections (10 µm thick), obtained in a cryostat, were stained with Haematoxilin-Eosin to morphological and morphometric analysis. We calculated the smallest diameter from 100 white muscle fibres per animal in each group. White muscle fibers were grouped in three classes: <20, 20-50 and >50µm to evaluate hypertrophy and hyperplasia in pacu white skeletal muscle. MyoD gene expression was determined by using RT-PCR. All PCR products visualized in 1% agarose gels were cloned and sequenced. Juvenile and adult pacu fish skeletal muscle showed similar morphology, with mosaic pattern characterized by fibers with different diameters. The great number of muscle fibers with diameter inferior 20µm observed in juvenile fish confirms the active hyperplasic process. In adult fish, most fibers were over 50µm diameter and denote the more intense muscle fiber hypertrophy. MyoD mRNA level in the juvenile fish was higher compared to adult fish. A consensus partial sequence for MyoD gene (338 bases pairs) was obtained. This sequence showed similarity with various vertebrate species, including teleost fishes. Differential expression of MyoD gene observed in white muscle of pacu possibly is related to differences in growth patterns during the phases analysed, with predominance of hyperplasia in juveniles and hypertrophy in adult fish

ASSUNTO(S)

piaractus mesopotamicus fatores de regulação miogenica piaractus mesopotamicus myogenic regulatory factors skeletal muscle growth musculo esqueletico - crescimento proteina myod myod protein

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