Nepomuceno Denise Barguil, D'Ávila Pessoa Grasielle Caldas, Koerich Leonardo Barbosa, Pereira Marcos Horácio, Sant'Anna Mauricio Roberto Viana, Araújo Ricardo Nascimento, Gontijo Nelder Figueiredo
Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia/ICB, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
Insect Sci. 2022 Aug;29(4):1059-1070. doi: 10.1111/1744-7917.12980. Epub 2021 Dec 22.
The sand fly Lutzomyia longipalpis is the main vector of Leishmania infantum in the Americas. Female sand flies ingest sugar-rich solutions and blood, which are digested in the midgut. Digestion of nutrients is an essential function performed by digestive enzymes, which require appropriate physiological conditions. One of the main aspects that influence enzymatic activity is the gut pH, which must be tightly controlled. Considering second messengers are frequently involved in the coordination of tightly regulated physiological events, we investigated if the second messenger cAMP would participate in the process of alkalinization in the abdominal midgut of female L. longipalpis. In midguts containing the indicator dye bromothymol-blue, cAMP stimulated the alkalinization of the midgut lumen. Through another technique based on the use of fluorescein as a pH indicator, we propose that cAMP is involved in the alkalinization of the midgut by activating HCO3 transport from the enterocyte's cytoplasm to the lumen. The results strongly suggested that the carrier responsible for this process would be a HCO3 /Cl antiporter located in the enterocytes' apical membrane. Hematophagy promotes the release of alkalinizing hormones in the hemolymph; however, when the enzyme adenylyl cyclase, responsible for cAMP production, was inhibited, we observed that the hemolymph from blood-fed L. longipalpis' females did not stimulate midgut alkalinization. This result indicated that hormone-stimulated alkalinization is mediated by cAMP. In the present study, we provide evidences that cAMP has a key role in the control of intestinal pH.
沙蝇长须罗蛉是美洲婴儿利什曼原虫的主要传播媒介。雌性沙蝇摄取富含糖分的溶液和血液，这些物质在中肠中被消化。营养物质的消化是消化酶执行的一项基本功能，而消化酶需要适宜的生理条件。影响酶活性的主要因素之一是肠道pH值，必须对其进行严格控制。鉴于第二信使经常参与紧密调节的生理事件的协调过程，我们研究了第二信使环磷酸腺苷（cAMP）是否会参与雌性长须罗蛉腹部中肠的碱化过程。在含有指示剂溴百里酚蓝的中肠中，cAMP刺激了中肠腔的碱化。通过另一种基于使用荧光素作为pH指示剂的技术，我们提出cAMP通过激活从肠细胞细胞质到肠腔的HCO₃转运而参与中肠的碱化。结果强烈表明，负责这一过程的载体是位于肠细胞顶端膜的HCO₃/Cl逆向转运体。吸血促进了血淋巴中碱化激素的释放；然而，当负责产生cAMP的腺苷酸环化酶被抑制时，我们观察到吸食血液的雌性长须罗蛉的血淋巴并未刺激中肠碱化。这一结果表明，激素刺激的碱化是由cAMP介导的。在本研究中，我们提供了证据表明cAMP在肠道pH值的控制中起关键作用。
