Suppression of phagocytic cell function has been proposed as a possible mechanism for the enhanced sensitivity to certain infectious agents exhibited by animals exposed to the organochloride insecticide, dieldrin. In the present study, we examined the effects of dieldrin on superoxide production by glycogen-eli citedperitoneal neutrophils (PMNs) from the rat. Dieldrin caused a concentration-dependent increase in superoxide production by PMNs incubated in vitro at 37°C. Superoxide release was increased significantly with 10 μm dieldrin and reached a maximum of 17 nmol/10 min/2.0 × 106 PMNs at a dieldrin concentration of 35 μm. Preincubation of PMNs for 5 min at room temperature with a barely suprathreshold concentration of either phorbol 12-myristate 13-acetate (PMA) or N-formyl-l-methionyl-l-leucyl-l-phenylalanine (FMLP) enhanced dieldrin-stimulated superoxide release by as much as ninefold or threefold, respectively. Maximum enhancement was obtained with 10 μm dieldrin for both PMA and FMLP. Time course studies with PMA-pretreated cells revealed that the rate of superoxide release was dependent on the concentration of dieldrin. Extracellular calcium played an important role in dieldrin-stimulated superoxide release, since PMNs treated with dieldrin in the absence of extracellular calcium did not release superoxide. Also, pretreatment with calcium ionophore A23187 greatly enhanced superoxide release from dieldrin-stimulated PMNs. These results show that dieldrin has a stimulatory effect on superoxide release from rat PMNs in vitro and that this stimulation is dependent on extracellular calcium.
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