Effect of hypoxia and acidosis on the cytotoxicity of six metal(ligand)₄(rhodamine-123), complexes at normal and hyperthermic temperatures

Abstract

Several analogues of PtCl₄(Rh-123)₂ in which the metal may be Pt or Pd and the coordinated ligand may be -CI, -CN or -NO₂ were prepared and tested in cell culture with EMT-6 cells at normal (37°) and hyperthermic (42° and 43°) temperatures and various environmental conditions (normally oxygenated vs. hypoxic and pH 7.40 vs. pH 6.45). Pd is a much more reactive metal than Pt, while -CN and-NO₂ are more tightly bound ligands than is -CI. The goal of these studies was to define the complex with the least cytotoxicity at 37° and the greatest enhancement in cytotoxicity under hyperthermic conditions. The Pt complexes Pt(CN)₄(Rh-123)₂ and Pt(NO₂),(Rh-123)₂ were much less cytotoxic than PtCl₄(Rh-123)₂ under both normothermic and hyperthermic conditions. The Pd complexes were, in general, more cytotoxic than the corresponding Pt complexes. The level of metal (Pt or Pd) in the cells did not appear to be a major factor in the level of cytotoxicity obtained. Complexes which were not cytotoxic at 37° regardless of oxygenation level or pH did not become cytotoxic at hyperthermic temperatures. In conclusion, the optimal members of this series were the complexes with chloro ligands, indicating that aquation is probably a necessary step in the cytotoxic mechanism and cytotoxicity at 37° was necessary to obtain cytotoxicity at higher temperatures.

Key Words:

• Tetrachloroplatinate
• pH
• hypoxia