title: Intracellular pH regulation in unstimulated Calliphora salivary glands is Na+ dependent and requires V-ATPase activity.
abstract: Salivary gland cells of the blowfly Calliphora vicina have a vacuolar-type H(+)-ATPase (V-ATPase) that lies in their apical membrane and energizes the secretion of a KCl-rich primary saliva upon stimulation with serotonin (5-hydroxytryptamine). Whether and to what extent V-ATPase contributes to intracellular pH (pH(i)) regulation in unstimulated gland cells is unknown. We used the fluorescent dye BCECF to study intracellular pH(i) regulation microfluorometrically and show that: (1) under resting conditions, the application of Na(+)-free physiological saline induces an intracellular alkalinization attributable to the inhibition of the activity of a Na(+)-dependent glutamate transporter; (2) the maintenance of resting pH(i) is Na(+), Cl(-), concanamycin A and DIDS sensitive; (3) recovery from an intracellular acid load is Na(+) sensitive and requires V-ATPase activity; (4) the Na(+)/H(+) antiporter is not involved in pH(i) recovery after a NH(4)Cl prepulse; and (5) at least one Na(+)-dependent transporter and the V-ATPase maintain recovery from an intracellular acid load. Thus, under resting conditions, the V-ATPase and at least one Na(+)-dependent transporter maintain normal pH(i) values of pH 7.5. We have also detected the presence of a Na(+)-dependent glutamate transporter, which seems to act as an acid loader. Despite this not being a common pH(i)-regulating transporter, its activity affects steady-state pH(i) in C. vicina salivary gland cells.
authors.affiliation: University of Potsdam, Institute of Nutrition Science, Department of Biochemistry of Nutrition, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany. schewe@uni-potsdam.de
authors.forename: Bettina
authors.initials: B
authors.lastname: Schewe
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Blenau
authors.forename: Bernd
authors.initials: B
authors.lastname: Walz
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000468:Alkalies / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000595:Amino Acid Sequence; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism; D004175:Diptera / Q000187:drug effects / Q000378:metabolism*; D027341:Excitatory Amino Acid Transporter 1 / Q000737:chemistry / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D012146:Rest; D012469:Salivary Glands / Q000187:drug effects / Q000201:enzymology*; D012964:Sodium / Q000378:metabolism*; D012996:Solutions; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism*
chemical_list: D000468:Alkalies; D002712:Chlorides; D027341:Excitatory Amino Acid Transporter 1; D012996:Solutions; D000643:Ammonium Chloride; D018698:Glutamic Acid; D000584:Amiloride; D012964:Sodium; D025262:Vacuolar Proton-Translocating ATPases; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; C039614:ethylisopropylamiloride