Bhuvaneswaran C, Morris M D, Shio H, Fowler S
Department of Biochemistry, University of Arkansas for Medical Sciences, Little Rock 72205.
Am J Pathol. 1982 Aug;108(2):160-70.
Livers of NCTR-BALB/c mice, affected by excessive accumulation of cholesterol and phospholipid, were fractionated by sucrose density gradient centrifugation. Lysosomes of very low density (rho = 1.05 - 1.08) were found, which by electron microscopy appeared identical to the storage inclusions seen in fixed tissues. These lysosomes could be purified about 10-fold over the original homogenate, and represented 4% of the total protein and 30-40% of the liver acid hydrolase content. The preparations were nearly free of mitochondrial, endoplasmic reticulum, and plasma membrane contamination. The lysosomes were laden with cholesterol and phospholipid. Cholesterol (greater than 97% unesterified) accounted for half of the total lipid, and sphingomyelin accounted for another 20%. Phosphatidylcholine and phosphatidylethanolamine were also present in substantial quantities. All of the excess cholesterol and sphingomyelin of liver could be attributed to the low density lysosomes. Lysosomal acid sphingomyelinase activity, measured with a synthetic substrate, was found to be 10-60% of BALB/c mouse control levels in liver, spleen, and cerebellum, while two other lysosomal enzymes, N-acetyl-beta-glucosaminidase and beta-glucuronidase, were increased 2-8-fold in the same tissues. These data and the morphologic observations of the preceding paper establish that the disorder affecting NCTR-BALB/c mice is a lysosome storage disease. We propose several possible mechanisms to explain the cholesterol and phospholipid overloading of lysosomes. The specific gene defect remains to be established.
受胆固醇和磷脂过度积累影响的NCTR-BALB/c小鼠肝脏，通过蔗糖密度梯度离心进行分级分离。发现了极低密度（ρ = 1.05 - 1.08）的溶酶体，通过电子显微镜观察，其与固定组织中所见的储存包涵体相同。这些溶酶体可在原始匀浆基础上纯化约10倍，占总蛋白的4%，肝脏酸性水解酶含量的30 - 40%。制备物几乎不含线粒体、内质网和质膜污染。这些溶酶体富含胆固醇和磷脂。胆固醇（大于97%未酯化）占总脂质的一半，鞘磷脂占另外20%。磷脂酰胆碱和磷脂酰乙醇胺也大量存在。肝脏中所有过量的胆固醇和鞘磷脂都可归因于低密度溶酶体。用合成底物测量的溶酶体酸性鞘磷脂酶活性，在肝脏、脾脏和小脑中为BALB/c小鼠对照水平的10 - 60%，而另外两种溶酶体酶，N - 乙酰 - β - 氨基葡萄糖苷酶和β - 葡萄糖醛酸酶，在相同组织中增加了2 - 8倍。这些数据以及前文的形态学观察结果表明，影响NCTR - BALB/c小鼠的疾病是一种溶酶体储存疾病。我们提出了几种可能的机制来解释溶酶体中胆固醇和磷脂的过载。具体的基因缺陷仍有待确定。
