Sorensen J S, Turnbull C A, Dearing M D
Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
Physiol Biochem Zool. 2004 Jan-Feb;77(1):139-48. doi: 10.1086/378923.
Detoxification capacity of enzymes in the liver is thought to be the primary factor governing dietary toxin intake by mammalian herbivores. Recently, toxin absorption in the gut was proposed as an alternative process that also influences toxin intake. We examined the role of the gut in regulating toxin absorption by quantifying excretion of a plant secondary compound in the feces. We hypothesized that specialists have a greater capacity to reduce intestinal absorption of toxins than do generalists. To test this hypothesis, we compared fecal excretion of alpha-pinene in specialist (Neotoma stephensi) and generalist (Neotoma albigula) woodrats. Alpha-pinene is the most abundant monoterpene in Juniperus monosperma, which occurs in the natural diet of both woodrat species. Woodrats were fed alpha-pinene in diets containing juniper foliage for 3 wk and, in a separate experiment, were given a single oral dose of alpha-pinene. Feces were collected from animals at the end of each experiment and analyzed for alpha-pinene concentration using gas chromatography. Both woodrat species excreted unchanged alpha-pinene in the feces. However, specialist woodrats excreted 40% more alpha-pinene per unit ingested from a juniper diet and excreted nearly four times a greater percentage of an oral dose of alpha-pinene compared with generalists.
肝脏中酶的解毒能力被认为是决定哺乳动物食草动物饮食中毒素摄入量的主要因素。最近，肠道中的毒素吸收被认为是另一个影响毒素摄入的过程。我们通过量化粪便中一种植物次生化合物的排泄量，研究了肠道在调节毒素吸收中的作用。我们假设，与泛食性动物相比，专食性动物减少肠道毒素吸收的能力更强。为了验证这一假设，我们比较了专食性（斯蒂芬更格卢鼠）和泛食性（白喉更格卢鼠）林鼠粪便中α-蒎烯的排泄情况。α-蒎烯是单籽杜松中含量最丰富的单萜烯，这两种林鼠的自然饮食中都有单籽杜松。林鼠在含有杜松树叶的日粮中喂食α-蒎烯3周，在另一个实验中，给它们口服一剂α-蒎烯。在每个实验结束时收集动物的粪便，并使用气相色谱法分析α-蒎烯浓度。两种林鼠都在粪便中排泄出未变化的α-蒎烯。然而，与泛食性林鼠相比，专食性林鼠从杜松日粮中每摄入单位α-蒎烯，粪便中排泄出的α-蒎烯多40%，并且口服一剂α-蒎烯后，排泄出的α-蒎烯百分比几乎是泛食性林鼠的四倍。
