Inhibition of cell division by sodium chloroiridate

Sodium chloroiridate at 3 × 10⁻⁴ M irreversibly inhibits cell division of mammalian cells in culture. Cells so affected by this compound of iridium included 3T3, SV-40 transformed 3T3, HeLa, and a primary human embryo strain. Cells are blocked in the G1 stage of the cell cycle. Although DNA synthesis is blocked by this compound, RNA and protein synthesis continue, resulting in cells of very large size.