Hamet M
Ann Biol Clin (Paris). 1975;33(3):131-8.
Owing to the very low levels of adenine in the intracellular and extracellular compartments and its low excretion by the kidney, no method of estimation was, until now, sufficiently specific and sensitive to determine precisely quantities of the order of 1 nanomole. The method of "isotopic enzymatic kinetic dilution" proposed by Newsholme et Taylor, has been used. The kinetic conditions of the reaction catalysed by adenine-phosphoribosyltransferase are favourable, [in particular KM (adenine) is very low, about 2.1(-6) M] and are not very sensitive to the action of other effectors. The technique proposed permits one to determine quantities of adenine between 0.05 and 1.2 nmole, i.e. 0.007 to 0.16 mug, with a precision of about 5 p. cent. Easy to carry out, it is useful in large series. Normal values in man of adenine thus measured (15 adult subjects) were as follows: Plasma: 1.13 +/- 0.41 nmoles.ml(-1), i.e. 0.152 +/-0 0.055 mug.ml(-1). Red cells: 3.65 +/- 0.87 nmoles.ml(-1), i.e. 0.493 +/- 0.117 mug.ml(-1). Urine (24 hour excretion): 11.41 +/- 1.24 mumoles, i.e. 1.54 +/- 0.17 mg.
由于细胞内和细胞外间隙中的腺嘌呤水平极低，且肾脏对其排泄量也很低，到目前为止，还没有一种估算方法具有足够的特异性和敏感性来精确测定约1纳摩尔数量级的腺嘌呤量。采用了纽肖姆和泰勒提出的“同位素酶动力学稀释”方法。腺嘌呤磷酸核糖基转移酶催化的反应动力学条件很有利，[特别是米氏常数（腺嘌呤）非常低，约为2.1×10⁻⁶ M]，且对其他效应物的作用不太敏感。所提出的技术能够测定0.05至1.2纳摩尔之间的腺嘌呤量，即0.007至0.16微克，精度约为5%。该方法易于实施，适用于大量样本。通过这种方法测量的人体（15名成年受试者）腺嘌呤正常值如下：血浆：1.13±0.41纳摩尔·毫升⁻¹，即0.152±0.055微克·毫升⁻¹。红细胞：3.65±0.87纳摩尔·毫升⁻¹，即0.493±0.117微克·毫升⁻¹。尿液（24小时排泄量）：11.41±1.24微摩尔，即1.54±0.17毫克。
