Tubules Of Aedes Aegypti Research Articles

Eliciting Renal Failure in Mosquitoes with a Small-Molecule Inhibitor of Inward-Rectifying Potassium Channels

Mosquito-borne diseases such as malaria and dengue fever take a large toll on global health. The primary chemical agents used for controlling mosquitoes are insecticides that target the nervous system. However, the emergence of resistance in mosquito populations is reducing the efficacy of available insecticides. The development of new insecticides is therefore urgent. Here we show that VU573, a small-molecule inhibitor of mammalian inward-rectifying potassium (Kir) channels, inhibits a Kir channel cloned from the renal (Malpighian) tubules of Aedes aegypti (AeKir1). Injection of VU573 into the hemolymph of adult female mosquitoes (Ae. aegypti) disrupts the production and excretion of urine in a manner consistent with channel block of AeKir1 and renders the mosquitoes incapacitated (flightless or dead) within 24 hours. Moreover, the toxicity of VU573 in mosquitoes (Ae. aegypti) is exacerbated when hemolymph potassium levels are elevated, suggesting that Kir channels are essential for maintenance of whole-animal potassium homeostasis. Our study demonstrates that renal failure is a promising mechanism of action for killing mosquitoes, and motivates the discovery of selective small-molecule inhibitors of mosquito Kir channels for use as insecticides.

The distribution of cell types in the malpighian tubules of Aedes taeniorhynchus (Wiedemann) (Diptera : Culicidae)

We have developed a histological technique that allows all of the cells in the malpighian tubules of Aedes taeniorhynchus (Diptera : Culicidae) and a few other mosquitoes to be counted and identified to cell type. We used this technique to examine the number and distribution of primary and stellate cells. Tubules, taken from the 4th instar larvae, pupae, adult males, and adult females, were examined. The mosquitoes were reared as larvae in either 10% or 100% seawater. In all cases examined, the total number of cells composing a tubule was somewhat variable, but no correlation between cell number and developmental stage, environmental salinity, or adult sex was observed. Under all conditions examined, stellate cells compose a fairly constant 16–18% of the total cell population of the tubule. Stellate cells were absent from the tubules in a region near the point of attachment to the midgut. Similar distribution ratios of primary and stellate cells were observed in the tubules of Aedes aegypti, Culex tansalis, and Culiseta inornata. The significance of these findings to a previously proposed tole for stèllate cells in ion transport is discussed.

Differential effects of secretagogues on Na and K secretion in the Malpighian tubules ofAedes aegypti (L.)

1. Rates of fluid secretion were measured in isolated Malpighian tubules from adult female mosquitoes and the concentrations of Na, K and Cl in the secreted fluid were measured by electron probe analysis under control conditions and in the presence of the secretagogues dibutyryl cAMP or head extract. 2. Under control conditions tubules secreted fluid at an average rate of 0.8 nl/min. The principal solutes in secreted fluid were Na at 94 mM, K at 91 mM and Cl at 161 mM. 3. Dibutyryl cAMP (1 mM) stimulated the rate of fluid secretion ∼250% (to 2.9 nl/min), increased the [Na] of secreted fluid to 178 mM, decreased the [K] to 17 mM, and did not change the [Cl]. Consequently, the net effect of dibutyryl cAMP was a highly significant stimulation of Na, Cl, and water secretion with no significant change in the secretion of K. 4. An aqueous extract of mosquito heads (0.1 head/μl) also stimulated the rate of fluid secretion ∼250% (to 2.8 nl/min), but introduced no major changes in the composition of secreted fluid with the exception of a slight, though significant decrease in the [K] from 91 to 73 mM. Consequently, the net effect of the head extract was the highly significant stimulation of Na, K, Cl, and water secretion. 5. The different effects of dibutyryl cAMP and head extract on the secretion of cations suggest that Na secretion and K secretion can be regulated independently of one another. In vivo, such a separate regulation of Na and K secretion might be important in the maintenance of hemolymph Na and K concentrations, especially following a blood meal.