Pathways of Intestinal Absorption and Their Ecological Significance

一个广为流传的观点是，糖（d -葡萄糖）主要由肠道主动吸收。然而，派们有证据表明，鸟类可以吸收相当数量的另一种形式的葡萄糖，l -葡萄糖，这种葡萄糖被认为是被动吸收的，而不是主动吸收的。提出的研究验证了鸟类被动吸收l -葡萄糖的假设，以及大多数d -葡萄糖被动吸收的推断。这些研究还将确定鸟类肠道的被动吸收如何随水溶性分子的大小而变化，以及吸收的溶质是否发生在肠细胞之间或肠细胞之间。这些发现对生理学家、进化生物学家、毒理学家和生态学家都很重要。大多数糖被被动吸收的发现将是重要的，因为它将挑战关于营养吸收的主流生理学观点，以及目前在进化消化生理学中试图将吸收营养的生理能力与营养摄入量相匹配的分析。允许被动吸收的高肠通透性可能允许毒素从肠内的植物和动物物质中被吸收。在这种情况下，需要研究与自然毒素接触和解毒有关的生态成本，以及野生动物对人类生产的新一代水溶性除草剂和杀虫剂的敏感性。

Karasov 9723793 A widespread notion is that sugar (D-glucose) is mainly actively absorbed by the intestine. The Pi's have evidence, however, that birds can absorb considerable amounts of the other form of glucose, L-glucose, which is thought to be absorbed passively, not actively. The proposed studies test the assumption that L-glucose is absorption passively by birds, and the inference that most D-glucose absorption is passive. The studies will also determine how passive absorption by the avian intestine varies with size of water-soluble molecules, and whether the movement of absorbed solutes occurs across or between intestinal cells. The findings will be important to physiologists, evolutionary biologists, toxicologists, and ecologists. A finding that most sugar is absorbed passively would be important because it would challenge prevailing physiological ideas about nutrient absorption as well as current analyses in evolutionary digestive physiology that attempt to match the physiological capacity to absorb nutrients with nutrient intake. A high intestinal permeability permitting passive absorption might permit toxins to be absorbed from plant and animal material in the intestine. This scenario would beg research on the ecological cost associated with exposure and detoxication of natural toxins, and perhaps the sensitivity of wild animals to the new generation of water-soluble herbicides and pesticides produced by humans.