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Giant Muscle Fibres in Pigs with Different Ryr1 Genotype
Author(s) -
Fazarinc G.,
ČandekPotokar M.,
Uršič M.,
Vrecl M.,
Pogačnik A.
Publication year - 2002
Publication title -
anatomia, histologia, embryologia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.34
H-Index - 35
eISSN - 1439-0264
pISSN - 0340-2096
DOI - 10.1046/j.1439-0264.2002.00420.x
Subject(s) - ryr1 , myofibril , glycolysis , mitochondrion , ultrastructure , chemistry , biology , anatomy , sarcoplasm , skeletal muscle , endoplasmic reticulum , biochemistry , enzyme , ryanodine receptor
Summary This study examined the frequency, morphological and immunohistochemical characteristics of the giant fibres in the longissimus muscle of local Krško polje pigs with different Ryr1 genotypes. Giant fibres were round‐shaped and had significantly increased cross‐sectional area compared with normal muscle fibres. Only fast‐twitch glycolytic fibres were affected, usually showing enhanced succinate dehydrogenase activity. On the ultrastructural level, the dilation of the sarcoplasmic reticulum, swelling of mitochondria and destruction of myofilaments was observed. The incidence of giant fibres was the highest in Ryr1 dimutant pigs (Ryr1 nn), which also exhibited lower muscle pH1 than heterozygous (Ryr1 Nn) or pigs with the wild Ryr1 gene (Ryr1 NN). However, the giant fibres were also present in pigs free of Ryr1 gene mutation. Our results suggest that the giant fibre syndrome depends mostly upon the rate and intensity of early post‐mortem glycolysis, which results in acidity of muscle tissue. We suppose that the giant fibre formation is a result of excessive intracellular lactate accumulation in some fast‐twitch glycolytic fibres. This process could also explain the ultrastructural alterations and the consequent changes in the oxidative enzymes and myofibrillar ATPase staining pattern observed in our and some previous studies.