Powell D R, Rosenfeld R G, Baker B K, Liu F, Hintz R L
J Clin Endocrinol Metab. 1986 Nov;63(5):1186-92. doi: 10.1210/jcem-63-5-1186.
Somatomedin levels measured by radioreceptor assay (RRA) or RIA on acid-ethanol-extracted or unextracted serum from patients with uremia are quite variable relative to normal values. We have investigated whether compounds accumulating in uremic serum were interfering with these RRA and RIA measurements. Insulin-like growth factor I (IGF-I) and IGF-II were separated from carrier proteins by either Sephadex G-50 acid chromatography or acid-ethanol extraction. IGF-I was measured by RIA, and IGF-II was determined by rat placental membrane RRA. IGF-I levels in the acid-ethanol extracts of serum from eight uremic adults were only 50% of the levels found in seven normal subjects, and IGF-II levels in these uremic patients were 350% of normal values. However, these significant differences were not found when comparable serum samples were acid chromatographed rather than acid-ethanol extracted; instead, IGF-I levels were 343 +/- 168 (mean +/- SD) ng/ml in uremic patients and 325 +/- 54 ng/ml in normal subjects, while IGF-II levels were 780 +/- 215 ng/ml in uremic patients and 588 +/- 46 ng/ml in normal subjects. To determine whether compounds that interfere with somatomedin assays were present in the acid-ethanol extracts of uremic serum, we acid chromatographed these extracts and found that a compound eluting in the carrier protein fraction of the uremic extract artifactually decreased IGF-I levels measured by RIA and increased IGF-II levels measured by RRA. We also found that unsaturated carrier protein binding of IGF-I and IGF-II was significantly increased in the carrier protein fraction of uremic acid-ethanol extracts at the dilutions used for somatomedin assays. We conclude that acid chromatography of unextracted or acid-ethanol-extracted uremic serum is necessary to remove a compound, probably unsaturated carrier protein, which interferes with RIA of IGF-I and RRA of IGF-II. Once this compound is removed, serum IGF-I levels (RIA) in uremic patients are not different from normal, and serum IGF-II levels (RRA) are not lower than normal.
通过放射受体分析（RRA）或放射免疫分析（RIA）检测尿毒症患者经酸乙醇提取或未提取血清中的生长调节素水平，相对于正常值而言差异很大。我们研究了尿毒症血清中积累的化合物是否会干扰这些RRA和RIA检测。胰岛素样生长因子I（IGF-I）和IGF-II通过Sephadex G-50酸性色谱法或酸乙醇提取法与载体蛋白分离。IGF-I通过RIA检测，IGF-II通过大鼠胎盘膜RRA检测。8名尿毒症成年患者血清酸乙醇提取物中的IGF-I水平仅为7名正常受试者中所测水平的50%，而这些尿毒症患者中的IGF-II水平为正常值的350%。然而，当对可比血清样本进行酸性色谱分析而非酸乙醇提取时，未发现这些显著差异；相反，尿毒症患者的IGF-I水平为3（均值±标准差）ng/ml，正常受试者为325±54 ng/ml，而尿毒症患者的IGF-II水平为780±215 ng/ml，正常受试者为588±46 ng/ml。为了确定尿毒症血清的酸乙醇提取物中是否存在干扰生长调节素检测的化合物，我们对这些提取物进行了酸性色谱分析，发现尿毒症提取物载体蛋白部分洗脱的一种化合物会人为降低通过RIA检测的IGF-I水平，并增加通过RRA检测的IGF-II水平。我们还发现，在用于生长调节素检测的稀释度下，尿毒症酸乙醇提取物的载体蛋白部分中IGF-I和IGF-II的不饱和载体蛋白结合显著增加。我们得出结论，对未提取或经酸乙醇提取的尿毒症血清进行酸性色谱分析，对于去除一种可能是不饱和载体蛋白的化合物是必要的，该化合物会干扰IGF-I的RIA和IGF-II的RRA。一旦去除该化合物，尿毒症患者的血清IGF-I水平（RIA）与正常水平无异，血清IGF-II水平（RRA）也不低于正常水平。
