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First published online March 31, 2007
Journal of Experimental Biology 210, 1463-1471 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.001529

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A vacuolar-type H⁺-ATPase and a Na⁺/H⁺ exchanger contribute to intracellular pH regulation in cockroach salivary ducts

Carsten Hille^* and Bernd Walz

University of Potsdam, Institute of Biochemistry and Biology, Department of Animal Physiology, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam-Golm, Germany

Author for correspondence (e-mail: walz{at}uni-potsdam.de)

Accepted 12 February 2007

Cells of the dopaminergically innervated salivary ducts in the cockroach Periplaneta americana have a vacuolar-type H⁺-ATPase (V-ATPase) of unknown function in their apical membrane. We have studied whether dopamine affects intracellular pH (pH_i) in duct cells and whether and to what extent the apical V-ATPase contributes to pH_i regulation. pH_i measurements with double-barrelled pH-sensitive microelectrodes and the fluorescent dye BCECF have revealed: (1) the steady-state pH_i is 7.3±0.1; (2) dopamine induces a dose-dependent acidification up to pH 6.9±0.1 at 1 µmol l^–1 dopamine, EC₅₀ at 30 nmol l^–1 dopamine; (3) V-ATPase inhibition with concanamycin A or Na⁺-free physiological saline (PS) does not affect the steady-state pH_i; (4) concanamycin A, Na⁺ -free PS and Na⁺/H⁺ exchange inhibition with 5-(N-ethyl-N-isopropyl)-amiloride (EIPA) each reduce the rate of pH_i recovery from a dopamine-induced acidification or an acidification induced by an NH₄Cl pulse; (5) pH_i recovery after NH₄Cl-induced acidification is almost completely blocked by concanamycin A in Na⁺-free PS or by concanamycin A applied together with EIPA; (6) pH_i recovery after dopamine-induced acidification is also completely blocked by concanamycin A in Na⁺-free PS but only partially blocked by concanamycin A applied together with EIPA. We therefore conclude that the apical V-ATPase and a basolateral Na⁺/H⁺ exchange play a minor role in steady-state pH_i regulation but contribute both to H⁺ extrusion after an acute dopamine- or NH₄Cl-induced acid load.

Key words: vacuolar H⁺-ATPase, V-ATPase, NHE, BCECF, intracellular pH, dopamine, biogenic amines, insect, cockroach, Periplaneta americana, salivary glands

This article has been cited by other articles:

				C. Hille and B. Walz Characterisation of neurotransmitter-induced electrolyte transport in cockroach salivary glands by intracellular Ca2+, Na+ and pH measurements in duct cells J. Exp. Biol., February 15, 2008; 211(4): 568 - 576. [Abstract] [Full Text] [PDF]