Relationship between oxidation and conjugation metabolism of skatole in pig liver and concentrations of skatole in fat.

High concentrations of skatole in fat of some intact male pigs are a major cause of boar taint. In this study, we investigated the effect of oxidative and conjugative metabolism of skatole in liver on the concentrations of skatole in the fat of intact male pigs. In Trial 1, 18 Yorkshire intact males were equally divided into two treatments with high (mean, .42; SD, .26 ppm) and low (mean, .06; SD, .02 ppm) fat skatole levels. There was an increased rate of skatole metabolism, an increased glucuronidation activity, and a decreased sulfation activity toward 2-naphthol in liver from pigs with high skatole levels (P < .05). In Trial 2, Swedish Yorkshire x F4 European Wild Pig intact males were used. Among skatole metabolites that were produced in incubations with liver microsomes, pro-MII was conjugated with glucuronic acid and sulfate, and metabolite F-1 was conjugated with glucuronic acid. The rates of formation of various skatole metabolites and conjugation of pro-MII were evaluated for 22 pigs with different levels of cytochrome P4502E1 in the liver. The formation of F-1 and sulfation of pro-MII were negatively correlated with fat skatole levels (r = -.59, and r = -.56, respectively) and were decreased in pigs with high fat skatole levels and low P4502E1 levels (P < .01). The results indicate that oxidation and conjugation reactions of skatole in pig liver have a dramatic effect on skatole levels in the fat. In particular, the formation of F-1 and formation and subsequent sulfation of pro-MII are related to low levels of skatole in the fat, presumably due to rapid metabolic clearance of skatole.