The potassium impermeable apical membrane of insect epithelia: a target for development of safe pesticides
Mem. Inst. Oswaldo Cruz
;
82(supl.3): 29-34, 1987. ilus
Article
in English
| LILACS
| ID: lil-623734
ABSTRACT
Columnar cell apical membranes (CCAM) in series with goblet cell apical membranes (GCAM) form an electroosmotic barrier separating the midgut lumen from epithelial cell cytoplasm. A unique K+ ATPase in GCAM generates three gradients across this barrier. A greater than 180 mV electrical gradient (lumen positive) drives amino acid uptake through voltage-dependent K+ symports. A greater than 1000-fold [H+] gradient (lumen alkaline) and a greater than 10-fold [K+] gradient (lumen concentrated) are adaptations to the high tannin and high K+ content, respectively, in dietary plant material. Agents which act on the apical membrane and disrupt the PD, H+, or K+ gradients are potential insecticides. Insect sensory epithelia and mammalian stria vascularis maintain similar PD and K+ gradients but would not be exposed to ingested anti-apical membrane insecticides. Following the demonstration by Sacchi et al. that Bacillus thuringiensis delta-endotoxin (Bt) induces specifically a K+ conductance increase in CCAM vesicles, we find that the K+ channel blocking agent, Ba2+, completely reverses Bt inhibition of the K+-carried short circuit current in the isolated midgut of Manduca sexta. Progress in characterizing the apical membrane includes finding that fluorosulfonylbenzoyladenosine binds specifically to certain GCAM polypeptides and that CCAM vesicles can be mass produced by Ca2+ or Mg2+ precipitation from Manduca sexta midgut.
Full text:
Available
Index:
LILACS (Americas)
Main subject:
Agriculture
/
Biological Control Agents
Limits:
Humans
Language:
English
Journal:
Mem. Inst. Oswaldo Cruz
Journal subject:
Tropical Medicine
/
Parasitology
Year:
1987
Type:
Article
/
Congress and conference
/
Project document
Affiliation country:
United States
Institution/Affiliation country:
Temple University/US
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