八眉猪和长白猪背最长肌肌纤维及脂肪细胞的发育性变化

Developmental Changes of Myofiber of Longissimus Dorsi Muscle and Adipocytes in Bamei and Landrace Pigs

为研究不同经济类型猪(Sus scrofa)种肉质特性形成的规律,采集7日龄和180日龄八眉猪、长白猪皮下脂肪组织及背最长肌,制备石蜡切片,HE染色后测定皮下、肌内脂肪细胞直径和体积及肌纤维直径;实时荧光PCR检测背最长肌MyHC各亚型mRNA表达,分析肌纤维类型变化。结果表明:7日龄八眉猪与同龄长白猪相比,肌内脂肪细胞直径、体积和肌内脂肪含量无显著差异,但八眉仔猪皮下脂肪细胞显著增大。180日龄八眉猪脂肪细胞直径、体积和肌内脂肪含量均显著大于同龄长白猪的;长白仔猪肌纤维直径显著大于八眉仔猪的,180日龄长白猪皮下脂肪细胞直径和体积增加量明显高于八眉猪的;仔猪背最长肌MyHC IIa和IIx表达较丰富,180日龄时均显著降低,而MyHC IIb表达及比例显著提高,但长白猪比八眉猪有更大程度的IIx和IIa减少及IIb增加。以上结果提示,生长后期猪脂肪形成主要为脂肪细胞的肥大过程;从出生早期到生长后期八眉猪和长白猪肌纤维组成类型发生较大改变,肌纤维类型的转化模式相同,主要差异是不同类型转化量的变化。

To explore the formation of meat quality characteristics in different economical pigs(Sus scrofa), the subcutaneous adipose tissue and longissimus dorsi muscle(LM) from 7-days-old and 180-days-old Landrace and Bamei pigs were taken and the paraffin sections were prepared. The size of subcutaneous and intramuscular adipocytes, and muscle fiber diameter were measured after HE staining. The expression levels of MyHC in LM were detected by real-time PCR. The results showed that the diameter and volume of subcutaneous adipocytes was significantly greater in Bamei pigs than in Landrace at the age of 7 days old, while there were no significant differences in the size of intramuscular adipocytes and intramuscular fat(IMF) content.The diameter and volume of adipocytes and IMF content were significantly larger in Bamei pigs than in Landrace at the age of 180 days old, while the muscle fiber diameter of Landrace piglets was significantly larger than that of Bamei piglets. At the age of 180 days old, there was a greater increment in Landrace than in Bamei pigs;the expressions of MyHC IIa and IIx in LM muscle of piglets were abundant, which were significantly decreased at the age of 180 days old, while the expression and proportion of MyHC IIb were significantly increased. However, MyHC IIx and IIa decreased and IIb increased more in Landrace than in Bamei pigs. These results suggested that the adipogenesis in late growth period was mainly the hypertrophy of adipocytes. From early birth to late growth period, the composition types of muscle fibers in Landrace and Bamei pigs changed greatly, and the transformation pattern of muscle fiber types was the same in these breeds, and the main difference was the change amount of transformation among muscle fibers.