Patterns Of Myofiber Growth And Muscle Lipid Deposition And The Role Of Thyroid Hormones In Large Yellow Croakers

Large yellow croaker, one of the four economic marine fish in China, was employed in the present study to investigate the pattern of myofiber growth and fat deposition. Grow hormone receptor (GHR) and Thyroid hormone receptors (TRs) cDNA fragments of large yellow croaker were cloned for the first time. The relationship between the expressions of GHR and TRs mRNA and myofiber growth and fat deposition was discussed. The role of thyroid hormone and its receptors in the regulation of flesh quality was further elucidated by analyzing the correlations between physiological and biochemical parameters and muscle fat content in adult large yellow croaker.1 Myofiber diameter distribution and muscle fat contentTo compare the patterns of muscle fiber diameter distribution between large yellow croakers of different ages, 1- and 2-year-old large yellow croakers were sacrificed and epaxial muscle was sampled for measuring muscle fiber diameter by histological method. Fat content in epaxial muscle was measured with aether extraction. The results showed that the muscle fiber diameter in both ages followed unimodal distribution. Myofiber diameter of 1-year-old large yellow croaker was ranged between 200μm and 400μm while those of 2-year-old fish between 200μm and 500μm. 2-year-old fish displayed a wider range of myofiber diameter distribution than 1-year-old ones. There was a significant increase in average myofiber diameter from 1-year-old to 2-year-old large yellow croaker (p<0.01).2 Analysis of muscle fat content and fatty acid compositionFat content in epaxial muscle was measured with aether extraction in 2.5-year-old large yellow croakers. According to the muscle fat content, 20 fish were allocated to low fat...