Sidell B D
J Exp Zool. 1977 Feb;199(2):233-50. doi: 10.1002/jez.1401990208.
The concentration of cytochrome c in the skeletal muscle of the green sunfish (Lepomis cyanellus) increases with decreasing temperature of acclimation: 1.51 +/- 0.09, 1.17 +/- 0.03, and 0.98 +/- 0.07 nanomoles per gram wet weight from muscle of animals acclimated to 5 degrees, 15 degrees, and 25 degrees C, respectively. The roles of synthesis and degradation of cytochrome c during thermal acclimation were investigated by measurement of loss of specific radioactivity from cytochrome c and from total mitochondrial heme protein, and by analysis of the rate of change in concentration of cytochrome c. The radioisotope used was 14C-delta-aminolevulinic acid, a non-reutilizable heme precursor. At 25 degrees C, the half-life of cytochrome c was 7.1 days based on radioactivity measurements and 5.6 days based on change in concentration. Statistical analysis showed no significant difference in half-lives obtained by the two methods. The half-life of total mitochondrial heme protein was determined to be 5.7 days on the basis of radioactivity data, under the same conditions. No significant difference was found between the rate of turnover of the heme protein pool from mitochondria and either measurement for cytochrome c at 25 degrees C. At an acclimation temperature of 5 degrees C, the half-life of cytochrome c from skeletal muscle was 13.7 days based upon changes in concentration. At low acclimation temperature, radioactive label was retained in acid-soluble form by fish for many days, precluding measurement of half-life by this technique. Transfer of fish from 25 degrees to 5 degrees C resulted in a rapid decrease of approximately 40% in rates in synthesis of skeletal muscle cytochrome c, and a concomitant decrease in the degradation rate constant for this molecule of approximately 60%. The disproportionality in temperature-sensitivities of these two processes leads to an approximately 50% net increase in the concentration of cytochrome c during acclimation. In transfer from 5 degrees to 25 degrees C, the converse, rapid readjustments in synthetic and degradative parameters occur, resulting in the observed decrease in cytochrome c content.
蓝鳃太阳鱼（Lepomis cyanellus）骨骼肌中细胞色素c的浓度随驯化温度的降低而增加：分别来自驯化至5℃、15℃和25℃的动物肌肉，每克湿重的细胞色素c浓度为1.51±0.09、1.17±0.03和0.98±0.07纳摩尔。通过测量细胞色素c和总线粒体血红素蛋白的比放射性损失，以及分析细胞色素c浓度的变化率，研究了热驯化过程中细胞色素c的合成和降解作用。使用的放射性同位素是14C-δ-氨基乙酰丙酸，一种不可再利用的血红素前体。在25℃时，基于放射性测量，细胞色素c的半衰期为7.1天，基于浓度变化则为5.6天。统计分析表明，两种方法获得的半衰期没有显著差异。在相同条件下，基于放射性数据确定总线粒体血红素蛋白的半衰期为5.7天。在25℃时，线粒体血红素蛋白池的周转速率与细胞色素c的任何一种测量结果之间均未发现显著差异。在驯化温度为5℃时，基于浓度变化，骨骼肌细胞色素c的半衰期为13.7天。在低驯化温度下，放射性标记物以酸溶性形式在鱼体内保留许多天，因此无法用该技术测量半衰期。将鱼从25℃转移至5℃导致骨骼肌细胞色素c的合成速率迅速下降约40%，同时该分子的降解速率常数相应下降约60%。这两个过程对温度敏感性的不均衡导致驯化过程中细胞色素c的浓度净增加约50%。从5℃转移至25℃时，合成和降解参数会发生相反的快速重新调整，导致观察到的细胞色素c含量下降。
