Phillips J, Schulze-Specking A, Decker K
Biol Chem Hoppe Seyler. 1985 Dec;366(12):1123-30. doi: 10.1515/bchm3.1985.366.2.1123.
The content and accessibility of terminal sialic acid and galactose residues of rat hepatocytes in primary culture were determined by in situ labeling using either periodate or sialidase/galactose oxidase treatment followed by sodium borotritiide reduction. Rat erythrocytes which were used for comparison showed a strongly enhanced tritium incorporation into galactose after sialidase treatment. In contrast, with freshly prepared rat hepatocytes only a small amount of galactose labeling was achieved after sialidase treatment. The amount of galactose labeled following sialidase treatment increased with time in culture up to day 6 and roughly paralleled the increase of the total sialic acid content. Major changes of sialic acid-containing glycoconjugates were restricted to the gangliosides. There was a transient drop in surface labeling of ganglioside-associated sialic acid on the first day in culture. The specific radioactivity of the in situ-tritiated ganglioside-sialic acid also fell by 50% in this period. Between day 2 and 4, there was an increase in gangliosidesialic acid labeling but the specific radioactivity of the sialic acid remained constant. This indicates that newly synthesized gangliosides but not the preexisting ones were accessible to periodate oxidation. The data allow conclusions about turnover and topology of the sialic acid-containing glycolipids.
采用高碘酸盐或唾液酸酶/半乳糖氧化酶处理，随后用硼氢化三钠还原的原位标记法，测定了原代培养大鼠肝细胞末端唾液酸和半乳糖残基的含量及可及性。用于比较的大鼠红细胞经唾液酸酶处理后，其半乳糖的氚掺入量显著增加。相比之下，新鲜制备的大鼠肝细胞经唾液酸酶处理后，仅实现了少量的半乳糖标记。唾液酸酶处理后标记的半乳糖量在培养至第6天时随时间增加，且大致与总唾液酸含量的增加平行。含唾液酸糖缀合物的主要变化仅限于神经节苷脂。培养第一天，神经节苷脂相关唾液酸的表面标记出现短暂下降。在此期间，原位氚标记的神经节苷脂 - 唾液酸的比放射性也下降了50%。在第2天至第4天之间，神经节苷脂唾液酸标记增加，但唾液酸的比放射性保持恒定。这表明新合成的神经节苷脂可被高碘酸盐氧化，而预先存在的神经节苷脂则不能。这些数据有助于得出关于含唾液酸糖脂的周转和拓扑结构的结论。
