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Abstract Because the chemical structure of fumonisin B1 (FB1) has several structural features in common with the sphingoid bases, sphingosine and dihydro-sphingosine (sphinganine), we tested the hypothesis that the fumonisins might alter the normal cellular activity or the metabolism of endogenous free sphingoid bases. FB1 was found to be a potent inhibitor of de novo sphingolipid biosynthesis in vitro, its primary target being sphinganine N-acyl-transferase. This inhibition resulted in a decrease in the biosynthesis of sphingosine and an accumulation of free sphinganine, an intermediate in the de novo biosynthetic pathway for complex sphin-golipids. These findings led to the hypothesis that consumption of feed containing fumo|nisins should cause an increase in the ratio of free sphinganine to free sphingosine in tissues and serum. Data consistent with this hypothesis have been obtained from horses and pigs that consumed feed containing fumonisin-contaminated corn screenings and from rats fed feed supplemented with fumonisin-containing fungal culture materials or pure FBi. Thus, the ratio of free sphinganine to free sphingosine shows promise as a tissue, urine, or serum marker for animals consuming feed containing fumonisins. The present paper provides a detailed description of the extraction of free sphingoid bases and the liquid chromatographic method we used for determining the relative amounts of free sphingosine and free sphinganine in serum, urine, and various tissues of animals. Study results are summarized, and the ratio of free sphinganine to free sphingosine is discussed as a presumptive test for identifying animals consuming fumonisin-contami-nated feed.
Riley et al. (Tue,) studied this question.