Dados do Trabalho

Título

Na+/K+-ATPase activation by cAMP in the midgut of Lutzomyia longipalpis (Lutz & Neiva, 1912; Diptera: Psychodidae)

Introdução

Lutzomyia longipalpis (Lutz & Neiva, 1912) females have been intensively studied regarding the regulation of midgut pH. The mechanisms involved in pH regulation are complex, and some aspects remain to be clarified. The second messenger cAMP participates in midgut alkalinization required for blood digestion. Beyond midgut alkalinization, cAMP could be involved in the regulation of other physiological events during blood digestion, such as the stimulation of the Na+/K+-ATPase.

Objetivo(s)

Thus, we aimed to investigate the role of Na+/K+ -ATPase as an electrochemical potential generator and its modulation by the second messenger cAMP in adult L. longipalpis’ midgut.

Material e Métodos

To measure total Na+/K+-ATPase activity, midguts were incubated with ATP in the presence of different ions, and the total ATPase activity was measured by the dosage of inorganic phosphate ions released in the reaction medium (μmol PO4−3 h−1). To evaluate Na+/K+-ATPase activation by cAMP, midguts were preincubated with db-cAMP, or forskolin, and then incubated with ATP in the presence of different ions; ATPase activity was measured as described above.

Resultados e Conclusão

Total enzymatic activity is reduced from 1.55 ± 0.29 μmol PO4−3 h−1 in the control group to 0.36 ± 0.03 μmol PO4−3 h−1 (p< 0.0001) when ouabain, a specific Na+/K+ -ATPase inhibitor, was present in the reaction medium. Pretreatment with db-cAMP led to a significant increase in total ATPase activity, from 1.16 ± 0.2 μmol PO4−3 h−1 (control) to 1.5 ± 0.21 μmol PO4−3 h−1 (p< 0.0001) . An increase in activity was also observed when cAMP production was stimulated by forskolin. We found evidences that support that Na+/K+-ATPase is the main generator of an electrochemical potential across membranes in the midgut of female L. longipalpis, and also that its activity is positively regulated by cAMP. cAMP-mediated Na+/K+ -ATPase pump activity might be necessary to maintain the transport of the nutrients produced during blood digestion.

Palavras-chave

Lutzomyia longipalpis, pH, midgut, Na+/K+-ATPase, cAMP.