Kumon Y, Loose L D, Birbara C A, Sipe J D
Department of Biochemistry, Boston University School of Medicine, MA 02118, USA.
J Rheumatol. 1997 Jan;24(1):14-9.
There are 2 classes of serum amyloid A (SAA) protein, acute phase (A-SAA) and constitutive (C-SAA). Hepatic synthesis of A-SAA is dramatically upregulated by inflammatory cytokines, while C-SAA is constitutively produced in the absence of inflammation. A-SAA has been shown to attract monocytes, neutrophils, and T lymphocytes, but the function of C-SAA remains to be determined. SAA proteins have been found in both serum and synovial fluid (SF) of patients with rheumatoid arthritis (RA), but have not been characterized with respect to isoform distribution. We determined the relative distribution of A-SAA and C-SAA in serum and SF of patients with RA and compared their abundance to the classic acute phase response protein, C-reactive protein (CRP).
A-SAA (isoforms SAA1, SAA2) and CRP were measured by commercially available ELISA kits. ELISA were developed for C-SAA (SAA4) and apolipoprotein AI (apo AI) in paired serum and SF from 56 patients with RA.
Concentrations (mean +/- SD) of A-SAA (SAA1,2) in serum and SF are 124 +/- 247, 20 +/- 32 micrograms/ml; CRP 75 +/- 70, 33 +/- 37 micrograms/ml; C-SAA (SAA4) 106 +/-49, 91 +/- 39 micrograms/ml; and apo AI 1.19 +/- 0.32, 0.37 +/- 0.12 mg/ml, respectively. CRP correlated positively with A-SAA in serum or SF and negatively with apo AI in serum. There was no correlation with apo AI in SF. In contrast, there was no correlation between C-SAA and CRP, A-SAA, or apo AI in serum or in SF. Median concentrations of A-SAA in serum and SF (44, 10 micrograms/ml) and CRP (46, 20 micrograms/ml), respectively, markedly differed from the mean values, whereas median concentrations of C-SAA (104, 85 micrograms/ml) and apo AI (1.17, 0.37 mg/ml), respectively, did not.
C-SAA concentrations vary in serum and SF independently of A-SAA and CRP levels. The lower concentration of A-SAA relative to C-SAA and CRP in SF suggests that A-SAA could be selectively catabolized in SF or alternatively not well transported into the synovial space.
血清淀粉样蛋白A（SAA）有两类蛋白，即急性期（A-SAA）和组成型（C-SAA）。炎症细胞因子可显著上调肝脏中A-SAA的合成，而C-SAA在无炎症时持续产生。已表明A-SAA可吸引单核细胞、中性粒细胞和T淋巴细胞，但C-SAA的功能仍有待确定。在类风湿关节炎（RA）患者的血清和滑液（SF）中均发现了SAA蛋白，但尚未对其亚型分布进行特征描述。我们确定了RA患者血清和SF中A-SAA和C-SAA的相对分布，并将它们的丰度与经典急性期反应蛋白C反应蛋白（CRP）进行比较。
采用市售ELISA试剂盒检测A-SAA（亚型SAA1、SAA2）和CRP。针对56例RA患者配对的血清和SF中的C-SAA（SAA4）和载脂蛋白AI（apo AI）开发了ELISA法。
血清和SF中A-SAA（SAA1,2）的浓度（均值±标准差）分别为124±247、20±32微克/毫升；CRP分别为75±70、33±37微克/毫升；C-SAA（SAA4）分别为106±49、91±39微克/毫升；apo AI分别为1.19±0.32、0.37±0.12毫克/毫升。血清或SF中的CRP与A-SAA呈正相关，与血清中的apo AI呈负相关。与SF中的apo AI无相关性。相比之下，血清或SF中的C-SAA与CRP、A-SAA或apo AI之间均无相关性。血清和SF中A-SAA的中位数浓度（分别为44、10微克/毫升）和CRP（分别为46、20微克/毫升）与平均值明显不同，而C-SAA（分别为104、85微克/毫升）和apo AI（分别为1.17、0.37毫克/毫升）的中位数浓度则无差异。
C-SAA在血清和SF中的浓度变化与A-SAA和CRP水平无关。SF中A-SAA相对于C-SAA和CRP的浓度较低，这表明A-SAA可能在SF中被选择性分解代谢，或者转运到滑膜腔的效率不高。
