Richmond R C, Farrell N P, Mahtani H K
Department of Radiation Oncology, Dartmouth-Hitchcock Medical Center, Hanover, New Hampshire 03756.
Radiat Res. 1989 Dec;120(3):403-15.
A series of binuclear rhodium(II) tetracarboxylate complexes was examined for potentiation of radiation-induced killing of Salmonella typhimurium cells. Carboxylate bridging ligands were varied as formate, acetate, trifluoroacetate, and propionate. All complexes caused hypoxic non-dose-modifying radiation potentiation in that variable thresholds were obtained with the radiation dose response. In phosphate-buffered saline (PBS), decreasing threshold doses, i.e., increasing potentiating efficiencies, were seen in the order of acetate = trifluoroacetate less than propionate less than formate. Beyond the threshold dose, the degree of potentiation for all complexes in PBS approximated 12 times the degree of radiation sensitivity seen for the N2 baseline of the radiation dose-response curve. No radiation potentiation by Rh2 carboxylates was seen for fully oxic suspensions. Irradiation of cells in the absence of phosphate increased the efficiency as well as the degree of radiation potentiation. It is hypothesized that bacterial radiation potentiation is initiated by one-electron reduction of the Rh2 carboxylates, most likely involving the hydrated electron, followed then by formation of an active product. These events likely occur outside the bacterial cell.
研究了一系列双核铑（II）四羧酸盐配合物对辐射诱导鼠伤寒沙门氏菌细胞杀伤的增强作用。羧酸盐桥连配体分别为甲酸酯、乙酸酯、三氟乙酸酯和丙酸酯。所有配合物都导致缺氧条件下的非剂量修饰辐射增强，即辐射剂量响应存在不同的阈值。在磷酸盐缓冲盐水（PBS）中，阈值剂量降低，即增强效率增加，顺序为乙酸酯 = 三氟乙酸酯＜丙酸酯＜甲酸酯。超过阈值剂量后，PBS中所有配合物的增强程度约为辐射剂量响应曲线N2基线辐射敏感性程度的12倍。对于完全有氧的悬浮液，未观察到铑（II）羧酸盐的辐射增强作用。在无磷酸盐条件下照射细胞会提高辐射增强的效率和程度。据推测，细菌辐射增强是由铑（II）羧酸盐的单电子还原引发的，最有可能涉及水合电子，随后形成活性产物。这些事件可能发生在细菌细胞外。
