There is evidence from epidemiological and experimental studies that consumption of cruciferous vegetables reduces the incidence of cancer at several sites, Recommendations have been made that people increase their consumption of cruciferous vegetables, yet little is known regarding potentially toxic components of these vegetables. Indeed, recent studies at the Eppley Institute (Birt et al., 1986) showed an increased incidence of pancreatic cancer in hamster receiving a high fat diet containing 10% cabbage. The longterm effects of increased cruciferous vegetable consumption are not clear-cut. The proposed research will investigate one of the potentially toxic properties of cruciferous vegetables. When the tissue of these vegetables is injured, thiocyanate ion, a catalyst of nitrosamine formation, is produced. We propose to examine the hypothesis that dietary thiocyanate, derived from consumption of cruciferous vegetables, specifically cabbage, can exert a significant catalytic effect on in vivo nitrosamine formation. We will measure excretion of nnitrosoproline (NPRO) by rats and mice following administration of nitrite and proline. Animals will be fed a semipurified diet containing 10% dehydrated fresh or autolyzed cabbage for 1 week prior to treatment. Other groups of animals will receive thiocyanate ion, escorbic acid, or both in the diet prior to treatment with NPRO precursors. Serum and urinary levels of thicyanate will be monitored in all groups and thiocyanate and ascorbate concentrations in the diet will be measured. We will investigate thiocyanate pharmacokinetics following intravenous and oral administration of thiocyanate ion, and following oral administration of benzyl isothiocyanate, sinigrin, and airdried and freezedried cabbage. The influence of the simultaneous presence of thiocyanate and ascorbate on NPRO formation in vitro will be investigated. The results of these studies will provide a foundation for estimating potential risks associated with increased consumption of cruciferous vegetables.
