Chloride Channels in Apical Membrane Patches of Stellate Cells of Malpighian Tubules of Aedes Aegypti Available to Purchase

Stellate cells of Aedes aegypti Malpighian tubules were investigated using patch-clamp methods to probe the route of transepithelial Cl⁻ secretion. Two types of Cl⁻ channel were identified in excised, inside-out apical membrane patches. The first Cl⁻ channel, type I, had a conductance of 24 pS, an open probability of 0.816±0.067, an open time of 867±114 ms (mean ± S.E.M., four patches) and the selectivity sequence I⁻>Cl⁻⪢isethionate>gluconate. The I⁻/Cl⁻ permeability ratio was 1.48, corresponding to Eisenman sequence I. The type I Cl⁻ channel was blocked by 2,2′-iminodibenzoic acid (DPC) and niflumic acid {2-[3-(trifluoromethyl)anilo]nicotinic acid}. The removal of Ca²⁺ from the Ringer’s solution on the cytoplasmic side had no effect on channel activity. The second Cl⁻ channel, type II, had a conductance of 8 pS, an open probability of 0.066±0.021 and an open time of 7.53±1.46 ms (mean ± S.E.M., four patches). The high density and halide selectivity sequence of the type I Cl⁻ channel is consistent with a role in transepithelial Cl⁻ secretion under control conditions, but it remains to be determined whether these Cl⁻ channels also mediate transepithelial Cl⁻ secretion under diuretic conditions in the presence of leucokinin.