Minor R R
J Biol Chem. 1982 Sep 10;257(17):10400-13.
Tissue injury by radiolabeled amino acids may severely affect experimental results. In this report, 3H-, 14C-, and/or 35S-labeled proline, serine, lysine, and methionine at concentrations of 1 and 5 microCi/ml were shown to cause severe injury in organ cultures of embryonic rat lungs. This injury was evident by 6 h and was amplified by 4 days of culture. This injury was characterized with light and electron microscopy, with morphometric analysis of growth, and with quantitation of the total protein and DNA/lung. After 6 h with 5 microCi/ml of 14C- or 35S-amino-acid there were more signs of cell degeneration, and by 24 h the labeled lungs were smaller, showed more signs of cell degeneration and death, and contained 30 to 60% less new protein and DNA than control lungs. After 24 h with 5 microCi/ml of 14C- or 35S-amino-acid the total protein and DNA/lung began to decrease. This toxicity was directly proportional to the amount of intracellular decay of each isotope. With 14C- and 35S-amino-acids, lung growth slowed with approximately 100 disintegrations/cell/day (d/c/d), growth stopped with approximately 200 d/c/d, and atrophy occurred with approximately 300 d/c/d. Cell proliferation, cell differentiation, and bronchial branching continued through 4 days even though atrophy occurred with greater than 200 d/c/d. With 3H-amino-acids, growth slowed with approximately 200 d/c/d and stopped with approximately 400 d/c/d. However, no toxicity was evident with less than 60 d/c/d of 14C or 35S, or with less than 90 d/c/d of 3H. These data suggest that the amounts of intracellular decay of these weak beta-emitting isotopes should be strictly limited. Increasing amounts of tissue injury occurred with 14C or 35S at greater than 10,000 dpm/micrograms of DNA, and with 3H at greater than 20,000 dpm/micrograms of DNA.
放射性标记氨基酸造成的组织损伤可能会严重影响实验结果。在本报告中，浓度为1和5微居里/毫升的3H、14C和/或35S标记的脯氨酸、丝氨酸、赖氨酸和蛋氨酸在胚胎大鼠肺的器官培养中显示会造成严重损伤。这种损伤在6小时时就很明显，并在培养4天后加剧。通过光学显微镜和电子显微镜、生长的形态计量分析以及肺中总蛋白和DNA的定量对这种损伤进行了表征。在含有5微居里/毫升的14C或35S氨基酸培养6小时后，出现了更多细胞变性的迹象，到24小时时，标记的肺体积变小，显示出更多细胞变性和死亡的迹象，并且与对照肺相比，新蛋白和DNA含量减少了30%至60%。在含有5微居里/毫升的14C或35S氨基酸培养24小时后，肺中总蛋白和DNA开始减少。这种毒性与每种同位素的细胞内衰变量直接成正比。对于14C和35S氨基酸，当衰变率约为100次衰变/细胞/天（d/c/d）时肺生长减缓，当衰变率约为200 d/c/d时生长停止，当衰变率约为300 d/c/d时发生萎缩。即使当衰变率大于200 d/c/d时出现萎缩，细胞增殖、细胞分化和支气管分支在4天内仍持续进行。对于3H氨基酸，当衰变率约为200 d/c/d时生长减缓，当衰变率约为400 d/c/d时生长停止。然而，当14C或35S的衰变率小于60 d/c/d，或3H的衰变率小于90 d/c/d时，未观察到明显毒性。这些数据表明，应严格限制这些弱β发射同位素的细胞内衰变量。当14C或35S的衰变率大于10,000衰变/分钟/微克DNA，以及3H的衰变率大于20,000衰变/分钟/微克DNA时，组织损伤量会增加。
