Differences between genetic stocks of chickens in response to acute and delayed effects of an organophosphorus...

The influence of genotypes of the major histocompatibility complex (MHC) on susceptibility to acute and delayed effects of an organophosphorus ester was measured in adult White Leghorn chickens from lines differing in response to sheep red blood cell (SRBC) antigen. Chickens from lines selected for high (HA) or low (LA) antibody response to SRBC and homozygous for B13B13 or B21B21 genotypes at the MHC were administered a single subcutaneous injection of diisopropyl phosphorofluoridate (DFP) at dosages of 0, 0.25, 0.50, or 1.0 mg/kg body weight using corn oil as the carrier. Criteria for toxicological responses included clinical, biochemical, and pathological measures. Clinical signs of acute cholinergic poisoning and delayed neuropathy were dose related. Brain and blood cholinesterase and carboxylesterase activities were more sensitive to inhibition by DFP than were liver cholinesterase and carboxylesterase activities. Cholinergic signs 3 h after administration of DFP were more pronounced in line HA than in line LA chickens. Pathological evidence of delayed neuropathy 2 wk after DFP administration was also more evident in HA than LA chickens. Although less pronounced than that for lines, differences in neurotoxic manifestations following DFP administration were greater for chickens of B21B21 than B13B13 genotypes. Activity of A-esterases, which hydrolyze organophosphorus esters without being inhibited by them, was lower in plasma of line HA than line LA chickens. Differences among the genotypes in activity of other esterases were not found in chickens not receiving DFP. These results indicated that responses of chickens to the neurotoxicant DFP were influenced by the background genome of the chickens.