Department of Biochemistry, Antoni van Leeuwenhoek-Huis, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
J Membr Biol. 1972 Dec;9(1):83-104. doi: 10.1007/BF01868045.
Plasma membranes were isolated under hypotonic conditions from rat and mouse livers and five hepatomas, i.e. one rather anaplastic rat hepatoma (and its subline) and three well-differentiated mouse hepatomas. All these membranes contained some 25% protein soluble in 0.15M NaCl. Evidence is presented that this protein is mainly, if not exclusively of nonmembranous origin. Protein/phospholipid P (P=phosphorus) ratios did not differ significantly for the various plasma membrane species except the rat-hepatoma subline, which showed a markedly lower ratio and was thus identified. Hepatoma membranes contained more P of a nonphospholipid nature than did liver membranes and to this increase contributed in all instances an increased RNA content and in some cases also an increased DNA content. The presence of DNA in these plasma membranes is artefactual, but that of RNA is more complicated. Artefactually, Ca(2+)-associated RNA of low mol wt and soluble in 0.15M NaCl, and residual RNA (genuine?, in liver membranes less than 1% in respect of protein) have been demonstrated. The increase in hepatoma-membrane RNA is attributed to the ribosomal RNA of the few microsomal vesicles which are structurally connected with these plasma membranes. The sialic acid content and the percentage of neuraminidase-resistant sialic acid of hepatoma as compared with liver membranes was either similar or changed, depending on the hepatoma strain. Gelfiltration of trypsin-released peptides of liver plasma membranes showed hexosamine and hexose to be confined to the sialic acidcontaining fractions. In spite of quantitative differences among fractions, the relative contents of the three carbohydrates in the combined fractions were (about) similar to those in intact liver membranes. Similar experiments with the rat-hepatoma membranes showed a changed carbohydrate expression.
质膜在低渗条件下从大鼠和小鼠肝脏以及五种肝癌中分离出来，即一种相当去分化的大鼠肝癌（及其亚系）和三种分化良好的小鼠肝癌。所有这些膜都含有约 25%可溶于 0.15M NaCl 的蛋白质。有证据表明，这种蛋白质主要（如果不是唯一的话）来自非膜来源。除了大鼠肝癌亚系外，各种质膜种类的蛋白质/磷脂 P（P=磷）比值没有显著差异，该亚系表现出明显较低的比值，因此可以识别。肝癌膜比肝膜含有更多的非磷脂性质的 P，这种增加归因于所有情况下 RNA 含量的增加，在某些情况下还归因于 DNA 含量的增加。这些质膜中 DNA 的存在是人为的，但 RNA 的存在则更为复杂。人为地，已经证明了与 Ca(2+)结合的低分子量、可溶于 0.15M NaCl 的 RNA 和残留 RNA（真正的？在肝膜中，相对于蛋白质，不到 1%）。肝癌膜中 RNA 的增加归因于与这些质膜结构上相连的少数微粒体小泡的核糖体 RNA。与肝膜相比，肝癌的唾液酸含量和神经氨酸酶抗性唾液酸的百分比要么相似，要么改变，这取决于肝癌株。用胰蛋白酶释放的肝质膜肽进行凝胶过滤显示，己糖胺和己糖仅限于含唾液酸的级分。尽管级分之间存在定量差异，但三种碳水化合物在组合级分中的相对含量（约）与完整肝质膜中的相似。用大鼠肝癌膜进行的类似实验显示出碳水化合物表达的改变。
