Christie N T, Owenby R K, Jacobson K B, Hiatt V S, Farkas W R
Biochim Biophys Acta. 1982 Oct 29;699(1):40-8. doi: 10.1016/0167-4781(82)90169-5.
Dietary cadmium causes the queuine-containing, Q(+), isoacceptors to increase relative to the guanine-containing, Q(-), ones of tRNATyr, tRNAHis and tRNAAsp of Drosophila melanogaster. Of the other divalent cations examined, Sr2+, Ni2+, Cu2+, Zn2+ and Hg2+, only Hg2+ failed to cause an increase in Q(+)tRNATyr. For these results, all pre-adult stages of the organism were spent on media containing the divalent ions. Adult flies that had developed on a normal diet also responded to divalent ions; Hg2+ as well as Cd2+, Sr2+ and Zn2+ caused an increase in Q(+)tRNATyr in 4 days. Using adult flies, the rate of the response was measured; when placed on a Cd2+-containing diet, they formed significantly more Q(+)tRNATyr within 24 h as compared to adults on a normal diet. Whether the queuine is derived from the diet or from de novo synthesis is yet to be determined. Since the metal ions represent a range of values in the 'hard-soft' classification, different sites of reaction are expected, yet for Drosophila a common result is an alteration in the ratio of Q(+) and Q(-) isoacceptors of these tRNAs. The transition to Q(+)tRNA may be an early indication of the metabolic imbalances resulting from the presence of the divalent cation.
膳食镉会导致黑腹果蝇的含Q（雀嘌呤）的Q（+）同功受体相对于含鸟嘌呤的Q（-）同功受体在tRNATyr、tRNAHis和tRNAAsp中增加。在所检测的其他二价阳离子中，Sr2+、Ni2+、Cu2+、Zn2+和Hg2+，只有Hg2+未能使Q（+）tRNATyr增加。基于这些结果，生物体的所有成虫前期阶段都饲养在含有二价离子的培养基上。在正常饮食中发育的成年果蝇也对二价离子有反应；Hg2+以及Cd2+、Sr2+和Zn2+在4天内会使Q（+）tRNATyr增加。使用成年果蝇，测量了反应速率；与正常饮食的成年果蝇相比，当置于含Cd2+的饮食中时，它们在24小时内形成的Q（+）tRNATyr明显更多。雀嘌呤是来自饮食还是从头合成尚待确定。由于金属离子在“硬-软”分类中代表一系列值，预计会有不同的反应位点，但对于果蝇来说，一个共同的结果是这些tRNA的Q（+）和Q（-）同功受体比例发生改变。向Q（+）tRNA的转变可能是二价阳离子存在导致代谢失衡的早期迹象。
