Kolassa N, Stengg R, Turnheim K
Can J Physiol Pharmacol. 1977 Oct;55(5):1039-44. doi: 10.1139/y77-143.
The metabolism of adenosine, inosine, hypoxanthine, and adenine (labelled with 14C in the carbon 8 position) at a concentration of 5 X 10(-6) M was studied in isolated epithelium of guinea pig jejunum. When adenosine or adenine was added to the antiluminal side of the epithelium, two-thirds or one-half, respectively, of cellular radioactivity was incorporated into the nucleotide fraction, mainly in the form of adenine nucleotides. Nucleotides synthesis from inosine or hypoxanthine was significantly smaller than that from adenosine. By contrast, another metabolic patern was found after luminal administration of adenosine, inosine, or hypoxanthine: the incorporation rate into the nucleotide fraction was equally high and the label was recovered in IMP and adenine nucleotides to about the same extent with all three substrates. Purine riboside (10(-4) M) significantly depressed nucleotide formation from adenosine, with respect to IMP formation in particular, while no change was observed in inosine or hypoxanthine salvage. The results suggest compartmentation of the enzymes of purine metabolism within the intestinal mucosa. The significance of this conclusion with regard to the salvage pathway is discussed.
研究了浓度为5×10⁻⁶ M的腺苷、肌苷、次黄嘌呤和腺嘌呤（在碳8位用¹⁴C标记）在豚鼠空肠离体上皮中的代谢情况。当将腺苷或腺嘌呤添加到上皮的腔外侧时，细胞放射性的三分之二或二分之一分别以腺嘌呤核苷酸的形式掺入核苷酸部分。由肌苷或次黄嘌呤合成核苷酸的量明显少于由腺苷合成的量。相比之下，在向肠腔给予腺苷、肌苷或次黄嘌呤后发现了另一种代谢模式：掺入核苷酸部分的速率同样很高，并且在所有三种底物中，IMP和腺嘌呤核苷酸中的标记回收程度大致相同。嘌呤核苷（10⁻⁴ M）显著抑制了腺苷形成核苷酸的过程，尤其是相对于IMP的形成，而在肌苷或次黄嘌呤补救途径中未观察到变化。结果表明嘌呤代谢酶在肠黏膜内存在区室化。讨论了这一结论对补救途径的意义。
