F-actin levels but not actin polymerization are affected by triphenyltin in HL-60 cells

The toxin triphenyl tin (TPT), Sn(C6H5)3+ caused a rapid decrease in the F-actin content of promyelocytic human leukemia cells (HL-60) chemically differentiated to neutrophils. Prior incubation (2 min) of the cells with 10 μM TPT did not modify the extent of actin polymerization inducible either by a receptor-mediated stimulus (chemotactic peptide fMLP) or by a direct activator of G proteins (AIF4-). The inorganic tin salts SnCl4, and SnCl4 did not affect F-actin content or production of HL-60 cells. Microfilament thiol groups were not reduced by exposure of cells to TPT, but even increased. When F-actin was exposed to 10 μM triphenyltin in a cell-free system, the depolymerizing effect was not detectable. Thus, TPT does not affect cytoskeletal protein directly but depends for its toxicity on some other induced change, probably ionic/osmotic in the intac