Gastrointestinal metabolism and transport of pesticidal carbamates.

Published evidence pertaining to gastrointestinal absorption and metabolism of pesticidal carbamates will be reviewed. The major body of evidence will come form investigations conducted by the author on N-methylcarbamate pesticides with rats; few investigations directly involving the gastrointestinal system have been reported by other research groups. Results derived from in vitro and isolated in vivo preparations show that pesticidal carbamates are absorbed and metabolized by gastrointestinal tissues. Numerous gastrointestinal metabolites have been separated; some have been identified and their behavior in the gut characterized; these data will be included in the review to the extent they have been published. The absorptive and metabolic capacities of the gastrointestinal system vary from one region to another. The author draws from evidence obtained from in vitro and in vivo studies and proposes the events that occur between carbamate ingestion and the appearance of the compound and/or its metabolites in the portal blood or mesenteric lymph. In this endeavor, the author acknowledges that superimposition of the metabolic precursory substrate-product sequence on the sequential physiologic steps from ingestion to defecation produces a complex situation which is difficult if not impossible to study meaningfully by investigation of one tissue component at a time (i.e., epithelial uptake, epithelial metabolism, mucosal to serosal transport, etc.).