Berry M N, Mazzachi R D, Peake M J
Department of Biochemistry and Chemical Pathology, Flinders Medical Centre, Bedford Park, South Australia.
Wien Klin Wochenschr Suppl. 1992;192:5-11.
The principles and main features of enzymatic methods for the measurement of sodium, potassium, and chloride are reviewed and their performance compared with current procedures. Each method makes use of a relatively specific enzyme, catalysing a reaction whose rate is sensitive to the ion to be determined. Where the (S)0.5 of the enzyme for the ion is much lower than the assay concentration, the ion concentration may be reduced by a binding agent. Alternatively, a competitive inhibitor may be used to raise the (S)0.5 of the enzyme. In the case of chloride determination with amylase the (S)0.5 of the enzyme is raised by limiting the concentration of free calcium. In the measurement of potassium, interfering ions such as sodium are removed by binding with Kryptofix 221 and improvement in performance is also achieved by use of a bacterial pyruvate kinase less sensitive to sodium. The enzymatic methods are applicable to measurement of sodium, potassium and chloride in blood or urine with good precision, accuracy, and specificity. They can be used on mechanized or manual instruments. There appears to be minimal interferences from compounds found in normal or pathological serum or urine.
本文综述了测定钠、钾和氯的酶法的原理及主要特点，并将其性能与现有方法进行了比较。每种方法都利用一种相对特异的酶，催化一个对被测离子浓度敏感的反应。当酶对离子的半饱和浓度（S）0.5远低于测定浓度时，可用结合剂降低离子浓度。或者，可使用竞争性抑制剂提高酶的（S）0.5。在用淀粉酶测定氯的情况下，通过限制游离钙的浓度提高酶的（S）0.5。在测定钾时，通过与环糊精221结合去除干扰离子如钠，使用对钠不太敏感的细菌丙酮酸激酶也可提高性能。酶法适用于血液或尿液中钠、钾和氯的测定，具有良好的精密度、准确度和特异性。它们可用于自动化或手工仪器。正常或病理血清或尿液中的化合物对其干扰似乎极小。
