Expression of Peroxisome Proliferator-Activated Receptor gamma2(PPAR_γ2) mRNA in Muscle Tissues of Japanese Black Cattle

peroxisome proliferator-activated receptor gamma2（PPAR_γ2）は，核内レセプターの一種で，脂肪細胞分化の中 心的な役割を担っている．本研究では，育成期の飼養条件の違いが，黒毛和牛骨格筋におけるPPAR_γ2 mRNAの発現に及ぼす影響について検討した．牛群を濃厚飼料区（C区）と乾草区（R区）に分けて飼養した．C区では，分娩後3日目に母子分離後，人工哺乳を2ヵ月間行った後，濃厚飼料を中心とした飼養形態とした．R区では，分娩後3ヵ月齢まで草地内で親子放牧し，離乳後牛舎内で乾草のみで飼養した．骨格筋サンプルは，胸最長筋（LT）および大腿二頭筋（BF）よりニードルバイオプシーを用いて，5ヵ月齢および7ヵ月齢時に摘出された．摘出した骨格筋サンプルは，すみやかに液体窒素中で凍結後，total RNAの抽出を行った．得られたtotal RNAを用いて，RT-PCR反応を行い，PPAR_γ2 mRNAの発現を見た．5ヵ月齢時においては，C区においてLTおよびBFともにPPAR_γ2 mRNAの発現が認められたが，R区においてはその発現は認められないか低かった．7ヵ月齢時では，両処理区でPPAR_γ2 mRNA発現が認められたが，R区よりもC区の方で発現は高かった．以上の結果より，育成期の飼養形態の違いが，黒毛和種骨格筋におけるPPAR_γ2 mRNAの発現に影響を及ぼすことが示唆された．Peroxisome proliferator-activated receptor gamma2 (PPAR_γ2) is one of the nuclear receptors and is known as a main regulator of adipogenesis. In this study, we investigated the influence of the feeding system on the expression of PPAR_γ2 mRNA in muscle tissue of young Japanese Black cattle. Four animals were divided into two groups: one group was separated from the mother cows at 3 days and was raised by artificial nursing until 2 months of age. After that they were fed with high concentrate (group C). Another was raised and grazed with their mother cows until 3 months. After weaning, they were fed only with roughage (group R). Muscle tissues were taken from M. longissimus thoracis (LT) and M. biceps femoris (BF) by needle biopsy at 5 and 7 months of age. Total RNA was isolated with ISOGEN from these tissues. Using the total RNA, we carried out RT-PCR to measure the expression of PPAR_γ2 mRNA. At 5 months, high expressions of PPAR_γ2 mRNA were observed in LT and BF of group C. On the other hand, in group R, there were no or low expressions of PPAR_γ2 mRNA. At 7 months, in both groups, the expressions were observed and the expressions in group C were higher than those in group R. From these results, it was suggested that feeding system during calf might influence the expression of PPAR_γ2 mRNA in muscle tissue of Japanese Black cattle and be related to intramuscular adipogenesis