Polychlorinated biphenyls and dibenzofurans in patients with yusho and their toxicological significance: a review.

The rice oil ingested by the patients with yusho and their blood, liver, and adipose tissue were analyzed for individual congeners of polychlorinated biphenyls (PCBs) and polychlorinated dibenzofurans ( PCDFs ). The individual congeners identified were examined for accumulation in the liver of monkeys and rats, inducing activities of benzo[a]pyrene 3-hydroxylase, benzphetamine demethylase, and DT-diaphorase in rats, and gravimetric changes of the thymus and liver in rats. Among the six PCB congeners detected in yusho patients, 2,3,4,5,3',4'-hexa-CB seems to be the compound most related to yusho judging from its strong enzyme-inducing activities in the liver and the thymus atrophy and liver hypertrophy caused by feeding it to rats. PCDF congeners identified in the patients' tissues showed a stronger toxicity in rats than these PCBs, exhibiting stronger enzyme induction activities and gravimetric changes of the tissues. These PCDF congeners, especially 2,3,4,7,8-penta-CDF, were also very accumulative in the liver. Therefore, they are considered as the most important etiologic agents for the current symptoms and signs of yusho patients.