Marinello E, Pizzichini M, Guerranti R, Cinci G, Arezzini L, Porcelli B, Terzuoli L
Institute of Biochemistry and Enzymology, University of Siena, Italy.
Life Sci. 2001 Jan 26;68(10):1131-42. doi: 10.1016/s0024-3205(00)01015-8.
In our previous experiments on rat liver we found that 15' after intraperitoneal administration of 14C-formate the specific radioactivity of allantoin was always higher than that of uric acid. The present experiments have been carried out to interpret this unexpected result, which was only observed in liver and we studied: a) the incorporation of 14C-glycine into uric acid and allantoin; b) the effects of two competitive inhibitors of xanthine oxidase and uricase, oxonic acid and allopurinol respectively, on levels of uric acid and allantoin in liver and on their specific radioactivity after administration of labelled precursor. The results suggested: a) that under normal conditions, the formation of allantoin is so fast that it exceedes export from liver to serum, and thus the radioactivity of labelled precursors accumulates in allantoin; b) that when allopurinol or oxonic acid are administered, the rate of export exceeds that of allantoin formation and the incorporation of radioactivity into allantoin is lower; c) that not all the data, however, could be interpreted on this basis, but seems to require the existence of different pools of uric acid, which are transformed separately into allantoin.
在我们之前对大鼠肝脏进行的实验中，我们发现腹腔注射14C-甲酸15分钟后，尿囊素的比放射性总是高于尿酸。进行本实验是为了解释这一仅在肝脏中观察到的意外结果，我们研究了：a）14C-甘氨酸掺入尿酸和尿囊素的情况；b）两种黄嘌呤氧化酶和尿酸酶竞争性抑制剂，即分别为氧嗪酸和别嘌呤醇，对肝脏中尿酸和尿囊素水平及其在给予标记前体后比放射性的影响。结果表明：a）在正常情况下，尿囊素的形成速度非常快，以至于超过了从肝脏向血清的输出速度，因此标记前体的放射性在尿囊素中积累；b）当给予别嘌呤醇或氧嗪酸时，输出速度超过尿囊素的形成速度，并且放射性掺入尿囊素的量较低；c）然而，并非所有数据都能基于此得到解释，似乎需要存在不同的尿酸池，它们分别转化为尿囊素。
