DIFFERENCES BETWEEN GENETIC STOCKS OF CHICKENS IN RESPONSE TO ACUTE AND DELAYED-EFFECTS OF AN ORGANOPHOSPHORUS COMPOUND

The influence of genotypes of the major histocompatibility complex (MH C) on susceptibility to acute and delayed effects of an organophosphor us ester was measured in adult White Leghorn chickens from lines diffe ring in response to sheep red blood cell (SRBC) antigen. Chickens from lines selected for high (HA) or low (LA) antibody response to SRBC an d homozygous for B-13B-13 or B21B21 genotypes at the MHC were administ ered a single subcutaneous injection of diisopropyl phosphorofluoridat e (DFP) at dosages of 0, 0.25, 0.50, or 1.0 mg/kg body weight using co rn oil as the carrier. Criteria for toxicological responses included c linical, biochemical, and pathological measures. Clinical signs of acu te cholinergic poisoning and delayed neuropathy were dose related. Bra in and blood cholinesterase and carboxylesterase activities were more sensitive to inhibition by DFP than were liver cholinesterase and carb oxylesterase activities. Cholinergic signs 3 h after administration of DFP were more pronounced in line HA than in line LA chickens. Patholo gical evidence of delayed neuropathy 2 wk after DFP administration was also more evident in HA than LA chickens. Although less pronounced th an that for lines, differences in neurotoxic manifestations following DFP administration were greater for chickens of B21B21 than B-13B-13 g enotypes. Activity of A-esterases, which hydrolyze organophosphorus es ters without being inhibited by them, was lower in plasma of line HA t han line LA chickens. Differences among the genotypes in activity of o ther esterases were not found in chickens not receiving DFP. These res ults indicated that responses of chickens to the neurotoxicant DFP wer e influenced by the background genome of the chickens.