Autor(es): Coast, GM; Garside, CS; Webster, SG; Schegg, KM; Schooley, DA

Resumo: Mosquito natriuretic peptide (MNP), an uncharacterised peptide from the yellow fever mosquito, Aedes aegypti, acts via cyclic AMP to stimulate secretion of Na+-rich urine by opening a Na+ conductance in the basolateral membrane of Malpighian tubule principal cells. Corticotropin releasing factor (CRF)-related peptides and calcitonin (CT)-like diuretic peptides use cyclic AMP as a second messenger and were therefore considered likely candidates for MNP. BLAST searches of the genome of the malaria mosquito Anopheles gambiae, gave sequences for the CRF-related peptide Anoga-DH44 and the CT-like peptide Anoga-DH31, which were synthesised and tested for effects on Malpighian tubules from An. gambiae and Ae. aegypti, together with 8-bromo-cyclic AMP.The cyclic AMP analogue stimulated secretion of Na+-rich urine by An. gambiae Malpighian tubules, reproducing the response to MNP in Ae. aegypti. It also depolarised the principal cell basolateral membrane voltage (V-b) while hyperpolarising the transepithelial voltage (V-t) to a similar extent. Anoga-DH44 and Anoga-DH31 stimulated production of cyclic AMP, but not cyclic GMP, by Malpighian tubules of An. gambiae. Both peptides had diuretic activity, but only Anoga-DH31 had natriuretic activity and stimulated fluid secretion to the same extent as 8-bromo-cyclic AMP. Likewise, Anoga-DH31 reproduced the effects of cyclic AMP on tubule electrophysiology, whereas Anoga-DH44 initially hyperpolarised V-b and depolarised Vt, which is the opposite of the effect of Anoga-DH31.Anoga-DH44 and Anoga-DH31 were also tested for effects on fluid secretion and ion transport by Ae. aegypti tubules. As in An. gambiae, the CRF-related peptide Anoga-DH44 had a non-specific effect on the transport of Na+ and K+, whereas the CT-like peptide Anoga-DH31 specifically stimulated transepithelial Na+ transport.We conclude that the CT-like peptide Anoga-DH31 is the previously uncharacterised mosquito natriuretic peptide.

Palavras-Chave: Malpighian tubules; Aedes aegypti; Drosophila melanogaster; Electrolyte transport; Fluid secretion; Conductance; Mechanisms; Diuresis; Leucokinin; Pathways

Imprenta: Journal of Experimental Biology , v. 208, n. 17, p. 3281-3291, 2005

Identificador do objeto digital: 10.1242/jeb.01760

Descritores: Aedes aegypti - Biochemistry ; Aedes aegypti - DNA

Data de publicação: 2005

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