| Description |
Herbivorous mammals use liver biotransformation enzymes to manage the highly toxic plant secondary compounds (PSC's) in their diets. Novel diets may require the use of different enzymes depending on the PSC composition. Woodrats (genus Neotoma) provide an exemplary model system for dietary studies, as there are many species that rely on various plants in diverse environments. To date, little work has been done to study Bryant's woodrat {Neotoma bryanti), some populations of which naturally consume creosote {Larrea tridentata), a plant with heavy chemical defenses. The main objective of this research was to compare liver enzyme quantity in two wild N bryanti populations when fed a control or 2% creosote diet. One population of woodrats lives outside of the creosote range, and is therefore naive to this diet, while the other commonly consumes creosote. Multiple proteins from three major biotransformation families were quantified using western blot: Cytochromes P450 (CYP), Catechol-O-methyl transferase (COMT), and Glutathione S-transferase (GST). In comparison to the naive population, the experienced population had constitutively lower s-COMT and GST-Ya, and higher CYP3A1 enzyme levels. In addition, there was a trend for a population and dietary treatment interaction in GST-Ya and s-COMT levels: animals experienced with creosote had lower enzyme concentrations when fed creosote, while naiVe animals had higher enzyme levels. These results suggest that over evolutionary time, selection within populations may have favored a decrease in expensive Phase II detoxification enzymes such as GST-Ya and s-COMT, in favor of less expensive enzymes such as CYP3A1 to adapt to creosote. |
