Species and sex differences in the reductive dechlorination of DDT by supplemented liver preparations

p,p′-DDT was converted to DDD, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane, by unheated 12,000g supernate supplemented with NADPH, made from liver of rat, mouse, hamster, quail, chicken and pigeon. The additional presence of exogenous riboflavin did not augment reduction. If, however, riboflavin was added to unheated microsomes supplemented with NADPH or NADH the rate of reduction was more than doubled.Heated 12,000g supernate, unsupplemented or containing only exogenous riboflavin, did not reduce DDT. When NAD(P)H was present, big species differences in activity occurred, the pigeon and cockerel scarcely reducing any DDT in 2 hr, the Wistar rat supernate being most active. Addition to heated 12,000g supernate of 30 μg riboflavin as well as NAD(P)H resulted in increased reductive activity for all six species. The species difference in effect of exogenous riboflavin between the pigeon and rat was also observed using four DDT analogs as substrates. A sex-related difference in activity of preheated, supplemented 12,000g supernate from livers of the chicken and Norwegian hooded rat was not found when unheated preparations were used. In contrast to the activity possessed by preheated 12,000g supernate of rat liver supplemented with NAD(P)H, similarly supplemented preheated microsomes did not reduce DDT. On adding riboflavin as well as NAD(P)H, however, preheated hepatic microsomes of both pigeon and rat produced DDD, and this activity was further increased by addition of unheated microsomal (105,000g) supernate. The biocatalytic system functioning in preheated preparations appears to need at least one component of heated microsomes, NAD(P)H and one or more water-soluble components.