H. Gagniere et al., Influence of genotype on contractile protein differentiation in different bovine muscles during foetal life, ANN ZOOTECH, 49(5), 2000, pp. 405-423
The purpose of this work was to compare muscle fibre differentiation in two
genetic types: "normal Charolais" and double-muscled (DM) "INRA 95" cattle
s displaying muscle hypertrophy. Six muscles with different contractile and
metabolic characteristics in adult animal: Masseter, Diaphragma (Di), Bice
ps femoris (BF), Longissimus thoracis, Semitendinosus and Cutaneus trunci (
CT) were excised from 60 to 260-day-old foetuses of both genotypes. These m
uscles present different degrees of hypertrophy in DM animals. Fibre types
were characterised by immunohistochemistry using monoclonal antibodies rais
ed against different myosin heavy chain isoforms. They were also studied by
SDS-PAGE electrophoresis, immunoblotting and ELISA methods. In both genoty
pes, foetal muscle development involved at least two generations of fibres
but their contractile differentiation was more or less delayed in double-mu
scled animals according to the muscle type. CT muscle, the most hypertrophi
ed in adults DM, showed the most important differences in the appearance of
the primary and secondary fibres in DM foetuses. It showed a delay of diff
erentiation which was made up during the last third of foetal life. Other m
uscles did not differ in the speed of appearance of the two generations of
fibres. They were originated from a higher proliferation of secondary fibre
s. Moreover, all DM muscles presented similar characteristics at 210 days o
f foetal life. These characteristics seem to be genetically determined. Jus
t before birth, muscles of double-muscled foetuses were composed of a great
er proportion of fast type Il fibres than normal animals. The most importan
t differences between genotypes were observed in BF and Di muscles.