Chloride channels in apical membrane patches of stellate cells of Malpighian tubules of Aedes aegypti.
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(-)(much greater than) isethionate>gluconate. The 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 Ca(2+) 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.
O'Connor
K R
KR
Department of Biomedical Sciences, VRT 8014, Cornell University, Ithaca, NY 14853, USA.
Beyenbach
K W
KW
D000330:Aedes / Q000378:metabolism* / Q000648:ultrastructure*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D018118:Chloride Channels / Q000378:metabolism*; D005260:Female; D008317:Malpighian Tubules / Q000378:metabolism* / Q000648:ultrastructure*; D008854:Microscopy, Electron; D018408:Patch-Clamp Techniques
D018118:Chloride Channels