Ghosh P, Okoh C, Liu Q H, Lakshman M R
Lipid Research Laboratory, D.V.A. Medical Center, Washington, D.C.
Alcohol Clin Exp Res. 1993 Jun;17(3):576-9. doi: 10.1111/j.1530-0277.1993.tb00802.x.
Transferrin is N-glycosylated glycoprotein and plays an important role in iron transport from sites of absorption and storage to sites of utilization. Chronic ethanol alters the normal microheterogeneity pattern of transferrin as a consequence of changes in the sialic acid content. However the underlying basis of this change in sialic acid contents of transferrin in alcohol abuse remains unclear. We have undertaken this study in order to investigate the effects of chronic ethanol in rats with respect to the hepatic rate of (i) transferrin synthesis based on labeled leucine incorporation, (ii) the incorporation of labeled N-acetyl mannosamine (NAM) into sialic acid residues of transferrin, and (iii) roles of specific sialyltransferase and sialidase at hepatic subcellular level. The results showed no significant difference in the incorporation of labeled leucine into transferrin at all levels between the control and ethanol group, whereas the incorporation of NAM into transferrin was significantly decreased by 84% (p < 0.001) both at the whole cell and Golgi level. Thus, the incorporation of labeled NAM relative to the incorporation of labeled leucine into hepatic transferrin was significantly decreased by 86% (p < 0.001) in chronic ethanol-treated animals as compared with the controls both at the whole cell golgi levels. These data are further supported by our finding of concomitant decrease in the activity of beta-galactoside alpha 2,6-sialyltransferase by 58% (p < 0.01) in ethanol-treated rats as compared with control animals.(ABSTRACT TRUNCATED AT 250 WORDS)
转铁蛋白是一种N-糖基化糖蛋白，在铁从吸收和储存部位转运到利用部位的过程中发挥着重要作用。慢性乙醇摄入会因唾液酸含量的变化而改变转铁蛋白正常的微观异质性模式。然而，酒精滥用中转铁蛋白唾液酸含量变化的潜在基础仍不清楚。我们开展这项研究，旨在调查慢性乙醇对大鼠肝脏转铁蛋白合成率（基于标记亮氨酸掺入）、标记的N-乙酰甘露糖胺（NAM）掺入转铁蛋白唾液酸残基以及特定唾液酸转移酶和唾液酸酶在肝脏亚细胞水平上的作用的影响。结果显示，对照组和乙醇组在各个水平上，标记亮氨酸掺入转铁蛋白的情况均无显著差异，而在全细胞和高尔基体水平上，NAM掺入转铁蛋白的量均显著降低了84%（p < 0.001）。因此，与对照组相比，在全细胞和高尔基体水平上，慢性乙醇处理的动物中，相对于标记亮氨酸掺入肝脏转铁蛋白，标记NAM的掺入量显著降低了86%（p < 0.001）。与对照动物相比，我们还发现乙醇处理的大鼠中β-半乳糖苷α2,6-唾液酸转移酶的活性伴随性降低了58%（p < 0.01），这进一步支持了这些数据。（摘要截短至250字）
