Verburg K M, Bowsher R R, Henry D P
Lilly Laboratories for Clinical Research, Eli Lilly & Co., Indianapolis, Ind.
J Allergy Clin Immunol. 1988 Sep;82(3 Pt 1):339-47. doi: 10.1016/0091-6749(88)90004-8.
The goals of this study were to evaluate the specificity of a new radioenzymatic assay for histamine when it is used for urinary-histamine determinations and to establish normal rates of urinary-histamine excretion for male and female subjects. Specificity of the assay was characterized by reacting urine samples at two different incubation temperatures and with varying amounts of highly purified histamine N-methyltransferase and S-adenosyl-L-[methyl-3H]methionine. The radiolabeled products were then separated by thin-layer chromatography and visualized by fluorescence-enhanced autoradiography. Our results indicate that at least one other substrate for histamine N-methyltransferase in addition to histamine is present in human urine, although the identity of this compound could not be determined. Optimization of enzyme-reaction conditions eliminated the methylation of this unidentified substrate while the methylation of histamine was maintained. The average urinary unidentified substrate while the methylation of histamine was maintained. The average urinary excretion of histamine determined for male subjects (N = 37) and female subjects (N = 111) was 18.7 micrograms/24 hr and 27.3 micrograms/24 hr, respectively. More than 12% of the normal female subjects examined had urinary-histamine excretion rates in excess of 50 micrograms/24 hr, which overlaps into the range previously considered to be indicative of abnormal mast cell secretion. In summary, this is the first radioenzymatic assay for histamine with documented specificity for the measurement of histamine in human urine.
本研究的目的是评估一种用于测定组胺的新型放射酶测定法在用于尿组胺测定时的特异性，并确定男性和女性受试者尿组胺排泄的正常速率。通过在两种不同的孵育温度下，用不同量的高度纯化的组胺N-甲基转移酶和S-腺苷-L-[甲基-³H]甲硫氨酸与尿样反应来表征该测定法的特异性。然后通过薄层色谱法分离放射性标记产物，并通过荧光增强放射自显影进行可视化。我们的结果表明，除组胺外，人尿中至少还存在一种组胺N-甲基转移酶的底物，尽管该化合物的身份无法确定。酶反应条件的优化消除了这种未鉴定底物的甲基化，同时保持了组胺的甲基化。在保持组胺甲基化的同时，未鉴定底物的平均尿排泄量。男性受试者（N = 37）和女性受试者（N = 111）测定的组胺平均尿排泄量分别为18.7微克/24小时和27.3微克/24小时。超过12%的正常女性受试者尿组胺排泄率超过50微克/24小时，这与先前认为指示异常肥大细胞分泌的范围重叠。总之，这是第一种用于组胺的放射酶测定法，其对人尿中组胺的测量具有已记录的特异性。
