Liver biotransforming enzymes in woodrats Neotoma stephensi (Muridae)

Mammalian herbivores are exposed to extremely high levels of plant secondary compounds naturally present in their diet. It has been speculated that specialist herbivores should express a unique pattern of biotransforming enzymes to permit the consumption of a single species of toxic plant. Specifically, specialists should rely on pathways that effectively biotransform the toxins they routinely encounter in their diet. We examined the hepatic mRNA expression and activity or content of biotransforming enzymes in the specialist herbivorous woodrat, Neotoma stephensi, and compared results to those of laboratory rats (Sprague-Dawley strain Rattus norvegicus). In addition, we investigated the role of α-pinene, a specific plant toxin present in the diet of N. stephensi on the mRNA expression pattern and activity or content of biotransforming enzymes in Sprague-Dawley rats. Overall, the levels of functionalization enzyme activity and mRNA were found to be higher in specialists, while glucuronidation enzyme activity and mRNA were lower. These results support predictions that specialist herbivores rely more on functionalization biotransformation pathways rather than glucuronidation pathways.