Low-dose dose-response for reduced cell viability after exposure of human keratinocyte (HEK001) cells to arsenite

摘要

Abstract The in vitro arsenite (AsIII) cytotoxicity dose-response (DR) of human keratinocytes (HEK001) was examined at greater statistical resolution than ever previously reported using the {MTT} assay to determine cell viability. Fifty-four 96-well plates were treated with AsIII concentrations of 0.25, 0.5, 1, 2, 3, 4, 5, 7, 10, 15, 20, 25, or 30 μM. Because of unexpected variation in viability response patterns, a two-stage {DR} analysis was used in which data on plate-specific viability (%), estimated as 100% times the ratio of measured viability in exposed to unexposed cells, were fit initially to a generalized lognormal response function positing that {HEK001} cells studied consisted of: a proportion P of relatively highly sensitive (HS) cells, a proportion Po of relatively resistant cells, and a remaining (1–P–Po) fraction of typical-sensitivity (TS) cells exhibiting the intermediate level of AsIII sensitivity characteristic of most cells in each assay. The estimated fractions P and Po were used to adjust data from all 54 plates (and from the 28 plates yielding the best fits) to reflect the condition that P = Po = 0 to provide detailed {DR} analysis specifically for {TS} cells. Four {DR} models fit to the combined adjusted data were each very predictive (R2 > 0.97) overall but were inconsistent with at least one of the data set examined (p 0.30) and exceeded 100% significance (p ≤ 10?6). A low-dose hormetic model provided the best fit to the combined adjusted data for {TS} cells (R2 = 0.995). Marked variability in estimates of P (the proportion of apparent {HS} cells) was unexpected, not readily explained, and warrants further study using additional cell lines and assay methods, and in vivo.