Santos Vânia C, Araujo Ricardo N, Machado Luciane A D, Pereira Marcos H, Gontijo Nelder F
Department of Parasitology, Federal University of Minas Gerais-UFMG, Avenue Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil.
J Exp Biol. 2008 Sep;211(Pt 17):2792-8. doi: 10.1242/jeb.019836.
Nutrient digestion and absorption after blood feeding are important events for Lutzomyia longipalpis, which uses these nutrients to produce eggs. In this context, the pH inside the digestive tract is an important physiological feature as it can markedly influence the digestive process as well as interfere with Leishmania development in infected phlebotomines. It was described previously that unfed females have an acidic midgut (pH 6). In this study, the pH inside the midgut of blood-fed females was measured. The abdominal midgut (AM) pH varied from 8.15+/-0.31 in the first 10 h post-blood meal to 7.7+/-0.17 after 24 h. While the AM was alkaline during blood digestion, the pH in the thoracic midgut (TM) remained acidic (5.5-6.0). In agreement with these findings, the enzyme alpha-glucosidase, which has an optimum pH of 5.8, is mainly encountered in the acidic TM. The capacity of unfed females to maintain the acidic intestinal pH was also evaluated. Our results showed the presence of an efficient mechanism that maintains the pH almost constant at about 6 in the midgut, but not in the crop. This mechanism is promptly interrupted in the AM by blood ingestion. RT-PCR results indicated the presence of carbonic anhydrase in the midgut cells, which apparently is required to maintain the pH at 6 in the midgut of unfed females. Investigations on the phenomenon of alkalization observed after blood ingestion indicated that two mechanisms are involved: in addition to the alkalization promoted by CO2 volatilization there is a minor contribution from a second mechanism not yet characterized. Some inferences concerning Leishmania development and pH in the digestive tube are presented.
吸血后营养物质的消化和吸收对长须罗蛉来说是重要事件，它利用这些营养物质来产卵。在此背景下，消化道内的pH值是一项重要的生理特征，因为它会显著影响消化过程，并干扰感染利什曼原虫的白蛉体内利什曼原虫的发育。此前有描述称未吸血的雌虫中肠呈酸性（pH 6）。在本研究中，对吸血雌虫中肠内的pH值进行了测量。腹部中肠（AM）的pH值在吸血后最初10小时内为8.15±0.31，24小时后为7.7±0.17。在血液消化过程中，腹部中肠呈碱性，而胸部中肠（TM）的pH值仍保持酸性（5.5 - 6.0）。与这些发现一致，最适pH值为5.8的α - 葡萄糖苷酶主要存在于酸性的胸部中肠。还评估了未吸血雌虫维持肠道酸性pH值的能力。我们的结果表明存在一种有效的机制，该机制能使中肠内的pH值几乎保持在6左右恒定，但嗉囊中则不然。这种机制在腹部中肠会因吸血而迅速中断。逆转录 - 聚合酶链反应（RT - PCR）结果表明中肠细胞中存在碳酸酐酶，这显然是未吸血雌虫中肠将pH值维持在6所必需的。对吸血后观察到的碱化现象的研究表明涉及两种机制：除了二氧化碳挥发促进的碱化外，还有一种尚未明确的第二种机制的较小贡献。文中还提出了一些关于利什曼原虫在消化管中的发育与pH值的推断。
