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First published online May 21, 2007
Journal of Experimental Biology 210, 1986-1991 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.004291

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Allatotropin-like peptide released by Malpighian tubules induces hindgut activity associated with diuresis in the Chagas disease vector Triatoma infestans (Klug)

Maria Soledad Santini and Jorge Rafael Ronderos^*

Centro Regional de Estudios Genomicos (CREG-UNLP) and Catedra Histol. Embriol. Animal (FCNyM-UNLP), La Plata, Argentina

View larger version (31K): [in this window] [in a new window]   Fig. 1. Myostimulatory activity of Aedes aegypti allatotropin (AT) on the hindgut (HG) of Triatoma infestans 4th-instar larvae. (A) Changes in the frequency of contraction induced by A. aegypti allatotropin. *Significant difference between pure AT applied at 10–18 mol l–1 and the other groups analysed (P0.05). Each bar represents the mean ± s.e.m. of the number of contractions m–1 in one of three experiments performed showing similar results (N=3–5 samples per treatment). (B) Image obtained from a hindgut preparation maintained in saline (Control). (C) The same preparation after treatment with pharmacological concentrations of pure A. aegytpi AT, showing a full and long-term contraction of the HG.

View larger version (22K): [in this window] [in a new window]   Fig. 2. (A) Elapsed time (seconds) necessary to release the hindgut (HG) content in in vitro preparations retaining different number of Malpighian tubules (MTs) undergoing an osmotic shock. Each bar represents mean ± s.e.m. of the elapsed time. Different letters (a–c) represent significant differences between samples in one of two experiments performed with similar results (N=3–6 samples per treatment; P0.05). (B) Aspect of the HG incubated with allatotropin (AT)-antiserum (1:100) undergoing an osmotic shock, after 3 h of the treatment (compare with the aspect of the HG under normal conditions in Fig. 1B). The same effect was obtained with three different preparations. (C) Elapsed time (seconds) until the beginning of the voiding in MTs–HG preparations retaining all MTs undergoing an osmotic shock, treated with different dilutions of the AT-antiserum [1:1000, 1:10 000, 1:100 000 and 1:1000 preadsorbed with 20 nmol of pure AT (P)]. Ctrl: samples without antiserum. Each bar represents mean ± s.e.m. of the elapsed time in one of two experiments performed with similar results (N=6 samples per treatment). Different letters (a–e) represent statistically significant differences between samples (P0.05). Note that preadsorbed samples are statistically different when compared with preparations treated with the same antiserum dilution (lower time), as well as with controls (higher). (D) Elapsed time (seconds) until the beginning of the voiding in MTs–HG preparations undergoing an osmotic shock. MTs were unattached and placed near the HG in the same diluted solution. Control, samples without antiserum; 1:1000, AT-antiserum dilution applied to the samples. Bars represent means ± s.e.m. *Significant differences between treatments (P0.05).

View larger version (16K): [in this window] [in a new window]   Fig. 3. In vivo blockade with allatotropin (AT)-antiserum of the AT-like peptide released by Malpighian tubules (MTs). Graphs represent the differences in the quantity of urine eliminated by insects injected with AT-antiserum (1:100), preadsorbed antiserum (1:100 plus 200 nmol of pure AT) or saline. (A) Urine eliminated at several time points after blood meal. (B) Accumulated volume of urine eliminated by groups with different treatments at several intervals after meal. (C) Comparison between treatments during the first 2 h after blood meal and during the next 22 h (2–24 h after blood intake). Each bar represents the mean ± s.e.m. of the volume of urine (N=4–6 samples per treatment). *Significant differences between insects injected with AT-antiserum and controls (saline and preadsorbed AT-antiserum). Data correspond to one of three experiments performed with similar results.