Table5_Digestive α-L-fucosidase activity in Rhodnius prolixus after blood feeding: effect of secretagogue and nutritional stimuli.docx

Introduction:Rhodnius prolixus (Hemiptera: Reduviidae) is an important vector of Trypanosoma cruzi, the causative agent of Chagas Disease. This insect is a model for the study of insect physiology, especially concerning the digestion of blood. Among the enzymes produced in the midgut of R. prolixus after blood feeding there is a α-L-fucosidase activity. There are very few studies on α-L-fucosidase of insects, and the role of R. prolixus α-L-fucosidase is still not clear. In this work, we tested if the mechanism for production of this enzyme is similar to the observed for proteases, a secretatogue mechanism that respond to the protein contents of the meal.
Methods: We tested if specific proteins or sugars elicit this response, which may help to understand the nature of the physiological substrate for this enzyme.
Results: In general, our results showed that the Anterior Midgut was the only midgut fraction that responds to the blood meal in terms of α-L-fucosidase production. Besides that, this response was not triggered by midgut distension or by ingestion of the blood cell fraction. Conversely, the enzyme was produced after feeding with the plasma fraction. However, the production of α-L-fucosidase was also triggered by different biochemical stimuli, as protein or fucoidan ingestion.
Discussion: This suggested that the production of the enzyme in the anterior midgut was a general physiological response under control of different convergent signals. Besides that, the comparison between different treatments for artificial blood feeding showed that heparinated blood was the choice with minor side effects for the study of the midgut α-L-fucosidase, when compared to defibrinated or citrated blood.

引言：长红锥蝽（Rhodnius prolixus，半翅目（Hemiptera）、猎蝽科（Reduviidae））是克氏锥虫（Trypanosoma cruzi）的重要传播媒介，而克氏锥虫正是恰加斯病（Chagas Disease）的致病原。该昆虫是昆虫生理学研究，尤其是血液消化机制研究的经典模式生物。在长红锥蝽吸血后中肠产生的各类酶中，存在α-L-岩藻糖苷酶（α-L-fucosidase）活性。目前针对昆虫α-L-岩藻糖苷酶的研究极少，长红锥蝽的该酶功能仍未明确。本研究探究了该酶的合成调控机制是否与蛋白酶类似——即响应进食餐食中蛋白质含量的分泌调控机制。

方法：本研究通过检测特定蛋白质或糖类是否可诱发该酶的表达响应，以期阐明该酶的生理性底物本质。

结果：总体而言，实验结果显示：前肠（Anterior Midgut）是唯一可在血液进食后诱导α-L-岩藻糖苷酶合成的肠段组分。此外，该酶的合成响应并非由肠腔扩张或摄入血细胞组分所触发。相反，摄入血浆组分则可诱导该酶的合成。不过，摄入蛋白质或岩藻聚糖（fucoidan）等不同生化刺激物也可触发α-L-岩藻糖苷酶的合成。

讨论：上述结果表明，前肠中该酶的合成是一种受多种趋同信号调控的一般性生理响应。此外，针对不同人工血液进食处理的对比研究显示：相较于去纤维蛋白血或枸橼酸化血液，肝素化血液是研究肠管α-L-岩藻糖苷酶时副作用最小的实验选择。