The Vacuolar-Type H+-ATPase in Ovine Rumen Epithelium is Regulated by Metabolic Signals

In this study, the effect of metabolic inhibition (MI) by glucose substitution with 2-deoxyglucose (2-DOG) and/or application of antimycin A on ovine rumen epithelial cells (REC) vacuolar-type H(+)-ATPase (vH(+)-ATPase) activity was investigated. Using fluorescent spectroscopy, basal pH(i) of REC was measured to be 7.3 +/- 0.1 in HCO(3) (-)-free, glucose-containing NaCl medium. MI induced a strong pH(i) reduction (-0.44 +/- 0.04 pH units) with a more pronounced effect of 2-DOG compared to antimycin A (-0.30 +/- 0.03 versus -0.21 +/- 0.03 pH units). Treatment with foliomycin, a specific vH(+)-ATPase inhibitor, decreased REC pH(i) by 0.21 +/- 0.05 pH units. After MI induction, this effect was nearly abolished (-0.03 +/- 0.02 pH units). In addition, membrane-associated localization of vH(+)-ATPase B subunit disappeared. Metabolic control of vH(+)-ATPase involving regulation of its assembly state by elements of the glycolytic pathway could provide a means to adapt REC ATP consumption according to energy availability.