Toxicity of dipyridyl compounds and related compounds.

ABSTRACTFive dipyridyl isomers, 2,2′-, 2,3′-, 2,4′-, 3,3′-, and 4,4′-dipyridyl, are products resulting from the pyrolytic degradation of tobacco products and degradation of the herbicide paraquat, and therefore may be present in the environment. In this article, the toxicological properties of these dipyridyl isomers in humans and animals are reviewed. Epidemiological studies suggest that cancerous skin lesions in workers involved in the manufacturing of paraquat may be associated with exposure to dipyridyl compounds. Experimental animal studies suggest that dipyridyl isomers may have several toxicological effects. Three of the dipyridyl isomers (the 2,2′, 2,4′, and 4,4′ isomers) appear to be inducers of some metabolic enzymes. The 2,2′-dipyridyl isomer, an iron chelator, appears to influence vasospasm in primate models of stroke. The cytotoxic effects of 2,2′-dipyridyl on several leukemia cell lines have been reported, and a potent teratogenic effect of 2,2′-dipyridyl has been observed in rats. Based on ...