HEMATOPOIETIC EFFECTS IN MICE EXPOSED TO DELTAMETHRIN AND HYDROCORTISONE

The effects of deltamethrin on bone marrow and spleen progenitor cell responsiveness to granulocyte and macrophage colony-stimulating factor s were evaluated. Deltamethrin was tested in parallel with hydrocortis one to further investigate some similarity in the in vivo effects of b oth compounds observed in previous studies in our laboratory. In vivo effects were studied after the subcutaneous administration in mice of three 5 mg/kg injections of deltamethrin and a single 30 mg/kg injecti on of hydrocortisone to Balb/c mice. Soft agar colony formation, marro w and spleen cell counts body, spleen and thymus weights were determin ed. Data obtained in vivo indicate that deltamethrin and hydrocortison e reversibly increase the formation of granulocyte and macrophage colo nies in the marrow, but not in the spleen. No changes were observed in total and differential cell counts in the marrow and spleen and splee n weights. Treatment with both compounds, however, resulted in a drama tic reduction in thymus weights. Assays for endotoxin demonstrate that these effects were not due to the liberation of endotoxin. In vitro a ddition of 10(-5), 10(-6) and 10(-7) M deltamethrin and hydrocortisone to marrow cultures from untreated mice resulted in different effects from those observed in vivo. Hydrocortisone increased granulocyte and reduced macrophage colonies, whereas deltamethrin was without in vitro effects. It is suggested that deltamethrin effects are due to an indi rect action on the hypothalamic - pituitary axis leading to increased corticosteroid levels. The importance of biotransformation mechanisms is also emphasized.