Fazarinc G, Candek-Potokar M, Ursic M, Vrecl M, Pogacnik A
Institute of Anatomy, Histology and Embryology, Veterinary Faculty, University of Ljubljana, Ljubljana, Slovenia.
Anat Histol Embryol. 2002 Dec;31(6):367-71. doi: 10.1046/j.1439-0264.2002.00420.x.
This study examined the frequency, morphological and immunohistochemical characteristics of the giant fibres in the longissimus muscle of local Krsko 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.
本研究检测了不同Ryr1基因型的当地克尔斯科波列猪最长肌中巨大纤维的频率、形态学和免疫组织化学特征。巨大纤维呈圆形，与正常肌纤维相比，其横截面积显著增大。仅快肌糖酵解纤维受到影响，通常表现为琥珀酸脱氢酶活性增强。在超微结构水平上，观察到肌浆网扩张、线粒体肿胀和肌丝破坏。巨大纤维的发生率在Ryr1双突变猪（Ryr1 nn）中最高，其肌肉pH1也低于杂合子（Ryr1 Nn）或具有野生型Ryr1基因的猪（Ryr1 NN）。然而，无Ryr1基因突变的猪中也存在巨大纤维。我们的结果表明，巨大纤维综合征主要取决于宰后早期糖酵解的速率和强度，这会导致肌肉组织酸化。我们推测巨大纤维的形成是一些快肌糖酵解纤维细胞内乳酸过度积累的结果。这一过程也可以解释我们和一些先前研究中观察到的超微结构改变以及氧化酶和肌原纤维ATP酶染色模式的相应变化。
