Biotransformation enzyme expression in the nasal epithelium of woodrats.

When herbivores come in contact with volatile plant secondary compounds (PSC) that enter the nasal passages the only barrier between the nasal cavity and the brain is the nasal epithelium and the biotransformation enzymes present there. The expression of two biotransformation enzymes Cytochrome P450 2B (CYP2B) and glutathione-S-transferase (GST) was investigated in the nasal epithelia and livers of three populations of woodrats. One population of Neotoma albigula was fed juniper that contains volatile terpenes. Juniper caused upregulation of CYP2B and GST in the nasal epithelium and the expression of CYP2B and GST in the nasal epithelium was correlated to liver expression, showing that the nasal epithelia responds to PSC and the response is similar to the liver. Two populations of Neotoma bryanti were fed creosote that contains less volatile phenolics. The creosote naive animals upregulated CYP2B in their nasal epithelia while the creosote experienced animals upregulated GST. There was no correlation between CYP2B and GST expression in the nasal epithelia and livers of either population. The response of the nasal epithelium to PSC seems to be an evolved response that is PSC and experience dependent.