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) c hemically differentiated to neutrophils. Prior incubation (2 min) of t he cells with 10 mu M TPT did not modify the extent of actin polymeriz ation inducible either by a receptor-mediated stimulus (chemotactic pe ptide fMLP) or by a direct activator of G proteins (AlF4-). The inorga nic tin salts SnCl2 and SnCl4 did not affect F-actin content or produc tion of HL-60 cells. Microfilament thiol groups were not reduced by ex posure of cells to TPT, but even increased. When F-actin was exposed t o 10 mu M triphenyltin in a cell-free system, the depolymerizing effec t was not detectable. Thus, TPT does not affect cytoskeletal protein d irectly but depends for its toxicity on some other induced change, pro bably ionic/osmotic in the intact cell.