Central role of the apical membrane H+-ATPase in electrogenesis and epithelial transport in Malpighian tubules

Klaus W. Beyenbach, Thomas L. Pannabecker, Wolfram Nagel

Research output: Contribution to journalArticle

54 Scopus citations

Abstract

The effects of bafilomycin A1, a blocker of V-type H+-ATPases, were investigated in Malpighian tubules of Aedes aegypti. Bafilomycin A1 reduced rates of transepithelial fluid secretion and the virtual short-circuit current (vI(sc)) with an IC50 of approximately 5 μmol l-1. As vI(sc) decreased, the electrical resistance increased across the whole epithelium and across the apical membrane, indicating effects on electroconductive pathways. Bafilomycin A1 had no effect when applied from the tubule lumen, pointing to the relative impermeability of the apical membrane of bafilomycin A1. Thus, bafilomycin A1 must take a cytoplasmic route to its blocking site in the proton channel of the H+-ATPase located in the apical membrane of principal cells. The inhibitory effects of bafilomycin A1 were qualitatively similar to those of dinitrophenol in that voltages across the epithelium (V(t)), the basolateral membrane (V(bl)) and the apical membrane (V(a)) depolarized towards zero in parallel. Moreover, V(bl) always tracked V(a), indicating electrical coupling between the two membranes through the shunt. Electrical coupling allows the H+-ATPase to energize not only the apical membrane, but also the basolateral membrane. Furthermore, electrical coupling offers a balance between electroconductive entry of cations across the basolateral membrane and extrusion across the apical membrane to support steady-state conditions during transepithelial transport.

Original languageEnglish (US)
Pages (from-to)1459-1468
Number of pages10
JournalJournal of Experimental Biology
Volume203
Issue number9
StatePublished - May 1 2000

Keywords

  • Aedes aegypti
  • Apical membrane
  • Bafilomycin
  • Dinitrophenol
  • Insect
  • Mosquito
  • Secretory epithelium
  • Short-circuit current
  • Vacuolar-type H-ATPase

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Physiology
  • Aquatic Science
  • Animal Science and Zoology
  • Molecular Biology
  • Insect Science

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