SELECTIVE MYELOTOXICITY OF PROPANIL

Propanil, a commonly used herbicide, has been previously shown to be i mmunotoxic for selected immune functions as well as specific cell type s, such as the macrophage. Propanil has also been shown to cause a met hemoglobulinemia and anemia through direct action on the erythrocyte. Demonstrated toxicity to both macrophages and erythrocytes raised conc ern for the possible myelotoxicity of propanil which could contribute to the observed effects of exposure. Therefore, the effect of propanil on several stem and progenitor cell types was assessed 7 days after a cute propanil exposure. The results described herein show that propani l, at doses of 50-200 mg/kg body wt, resulted in reduction in the numb er of myeloid stem cells and early myeloid and erythroid progenitor ce lls. No reduction in the numbers of more differentiated myeloid and er ythroid progenitor cells was noted at even the highest dose used (200 mg/kg). In addition, no statistically significant difference in number of leukocytes per femur was noted. These data suggest that propanil i s myelotoxic to early hemapoietic stem cells, but that this reduction is apparently compensated by proliferation of more differentiated prog enitor cells for the myeloid and erythroid lineages. It remains unknow n whether chronic exposure leads to progressive depletion of additiona l myeloid and erythroid cells. (C) 1994 Society of Toxicology.