INHIBITION BY PENTACHLOROPHENOL OF PRODUCTION OF REACTIVE-OXYGEN INTERMEDIATES BY MEDAKA PHAGOCYTIC BLOOD-CELLS

Phagocytes isolated from the pronephros of the Japanese medaka (Oryzias latipes) produce reactive-oxygen intermediates (ROI) that mediate various protective functions by virtue of their antimicrobial and antineoplastic properties. Pentachlorophenol (PCP) is a common marine and estuarine contaminant that is bioconcentrated in the tissues of exposed fish. This study shows that PCP exposure, at sublethal concentrations, produces a dose-dependent suppression of ROI generation by medaka phagocytes. Inhibition of phagocytosis-associated ROI detected by nitroblue-tetrazolium (NBT) reduction was seen after 20 h of PCP exposure, or after only 1 h of exposure by using luminol-augmented chemiluminescence (CL). The inhibition produced by pure PCP was slightly enhanced with dioxin-contaminated technical grade PCP. Inhibition of CL was reversible after the cells were placed in PCP-free medium. The data suggest that PCP exerts direct immunotoxicological effects on medaka blood cells.