Rosano T G, Lee S K, Jones D H
J Cell Biol. 1976 Jun;69(3):581-8. doi: 10.1083/jcb.69.3.581.
The activity of cytochrome oxidase (an inner mitochondrial membrane marker) in mouse mammary gland homogenates was found to increase five- to sixfold from late pregnancy to day 8 of lactation, while that of monoamine oxidase (an outer membrane marker) increased only about 25%. The specific activity of cytochrome oxidase in the isolated mitochondria decreased slightly over the same period while the specific activity of monoamine oxidase decreased fivefold. This reflects the fact that both cytochrome oxidase and mitochondrial protein are increasing at a much greater rate than is monoamine oxidase activity. Mixing experiments preclude the possibility that the release or removal of an inhibitor or stimulator produces the changes in enzymatic activity. The cytochrome oxidase to monoamine oxidase ratio was followed throughout the pregnancy-lactation cycle in total mammary homogenates, isolated mammary parenchymal cells, and isolated mammary mitochondria. In each preparation the pattern was the same with little change in the ratio until late pregnancy; and then a three- to fourfold increase occurred and the values reached a maximum by day 8 of lactation. These experiments were interpreted as demonstrating that the observed enzymatic changes are reflective of alterations in the mitochondria of the mammary parenchymal cell population. Electron micrographs of mid-pregnant and mid-lactating mammary parenchymal cells in situ were prepared, and distinct changes in the mitochondrial morphology noted. The most significant and obvious change is the large increase in the number of inner membrane cristae and an increase in matrix density in the lactating gland cell. Therefore, both enzymatic and morphological studies support the concept of an expansion of the mitochondrial inner membrane during presecretory differentiation in the mouse mammary parenchymal cell.
研究发现，从小鼠妊娠后期到泌乳第8天，其乳腺匀浆中细胞色素氧化酶（一种线粒体内膜标志物）的活性增加了五到六倍，而单胺氧化酶（一种外膜标志物）的活性仅增加了约25%。在同一时期，分离出的线粒体中细胞色素氧化酶的比活性略有下降，而单胺氧化酶的比活性下降了五倍。这反映出细胞色素氧化酶和线粒体蛋白的增加速率比单胺氧化酶活性的增加速率大得多。混合实验排除了抑制剂或刺激剂的释放或去除导致酶活性变化的可能性。在整个妊娠 - 泌乳周期中，对全乳腺匀浆、分离出的乳腺实质细胞和分离出的乳腺线粒体中的细胞色素氧化酶与单胺氧化酶的比率进行了跟踪。在每种制剂中，模式都是相同的，直到妊娠后期该比率几乎没有变化；然后增加了三到四倍，并在泌乳第8天达到最大值。这些实验被解释为表明观察到的酶变化反映了乳腺实质细胞群体中线粒体的改变。制备了妊娠中期和泌乳中期乳腺实质细胞的原位电子显微镜照片，并注意到线粒体形态有明显变化。最显著和明显的变化是泌乳期腺细胞内膜嵴数量大幅增加以及基质密度增加。因此，酶学和形态学研究都支持小鼠乳腺实质细胞在分泌前分化过程中线粒体内膜扩张的概念。
