Benson M D, Scheinberg M A, Shirahama T, Cathcart E S, Skinner M
J Clin Invest. 1977 Mar;59(3):412-7. doi: 10.1172/JCI108654.
Serum amyloid protein A (SAA), the precursor of secondary amyloid protein, is elevated in chronic diseases which are associated with an increased incidence of amyloid. However, SAA is also elevated in acute bacterial and viral infections and somes forms of cancer. The murine model of casein-induced amyloidosis was studied to determine the relationship between SAA production and amyloid deposition. SAA levels measured by radioimmunoassay were found to be as high as 200 times the normal level in CBA/J mice receiving daily parenteral casein. After a single injection of casein the SAA level was elevated by 3h and peaked by 12-18 h. Similar levels were found in casein-treated A/J mice, a strain less susceptible to the induction of amyloid. Parenterally administered bovine serum albumin, which has low potential for amyloid induction, gave SAA levels in CBA/J and A/J mice comparable to casein treatment. These data show that, while SAA levels are elevated during chronic antigenic stimulation, there are other factors involved in amyloid formation. These factors may include alterations in the degradation of SAA by the reticuloendothelial system caused by substances such as casein. Nude (athymic) mice were shown to attain high levels of SAA after receiving casein parenterally. Therefore, thymus-derived lymphocytes are not necessary for the synthesis of SAA.
血清淀粉样蛋白A（SAA）是继发性淀粉样蛋白的前体，在与淀粉样变发病率增加相关的慢性疾病中会升高。然而，SAA在急性细菌和病毒感染以及某些癌症形式中也会升高。研究了酪蛋白诱导的淀粉样变性小鼠模型，以确定SAA产生与淀粉样蛋白沉积之间的关系。通过放射免疫测定法测得，每日接受肠胃外注射酪蛋白的CBA/J小鼠体内的SAA水平高达正常水平的200倍。单次注射酪蛋白后，SAA水平在3小时时升高，并在12 - 18小时达到峰值。在酪蛋白处理的A/J小鼠中也发现了类似水平，A/J小鼠是一种对淀粉样变诱导较不敏感的品系。肠胃外注射诱导淀粉样变可能性较低的牛血清白蛋白后，CBA/J和A/J小鼠体内的SAA水平与酪蛋白处理相当。这些数据表明，虽然在慢性抗原刺激期间SAA水平会升高，但淀粉样变形成还涉及其他因素。这些因素可能包括酪蛋白等物质引起的网状内皮系统对SAA降解的改变。已证明裸（无胸腺）小鼠在肠胃外接受酪蛋白后会达到高水平的SAA。因此，胸腺来源的淋巴细胞对于SAA的合成不是必需的。
