The neuropeptide Rhopr CCHamide2 inhibits serotonin-stimulated transcellular Na+ transport across the anterior midgut of the vector of Chagas disease Rhodnius prolixus

CAPRIOTTI, NATALIA; GIOINO, PAULA; ONS, SHEILA; IANOWSKI, JUAN P.

JOURNAL OF EXPERIMENTAL BIOLOGY

COMPANY OF BIOLOGISTS LTD

Año: 2021

0022-0949

Rhodnius prolixus is a blood-feeding insect vector of Tripanosoma cruzi, a protozoan parasite that causes Chagas´ disease. During each blood meal the animals ingest large volumes of blood, that may be up to 12 times the unfed body mass. These blood meals impose a significant osmotic stress for the animals due to the hyposmotic condition of the ingested blood compared to the insect´s haemolymph. Thus, the insect undergoes a massive postprandial diuresis that allows for the excretion of the plasma fraction of the blood in less than two hours. Diuresis is performed by the excretory system, consisting of the Malpighian tubules and gut, under the control of diuretic and antidiuretic factors. We investigated the ion transport machinery triggered by stimulation with the diuretic factor serotonin in the anterior midgut (i.e. crop) and the effect of the diuretic modulator RhoprCCHamide2. Ussing chamber assays revealed that serotonin-stimulated increase in transepithelial short circuit current (Isc) was more sensitive to the blockage with amiloride than EIPA, suggesting the involvement of Na+ channels. Incubation in Na+-free, but not Cl−-free saline, blocked the effect of serotonin on Isc. Moreover, treatment with NKCC and NCC blockers had no effect on fluid secretion but was blocked by amiloride. Blockage of Na+/K+-ATPase with ouabain inhibit Isc but the H+-ATPase inhibitor bafilomycin had no effect. The neuropeptide RhoprCCHamide2 diminished serotonin-stimulated Isc across the crop. The results suggest that Na+ undergoes active transport via an apical amiloride-sensitive Na+ channels and a basolateral ouabain-sensitive Na+/K+-ATPase while Cl− is transported through passive paracellular pathway.