Differential involvement of vacuolar H(+)-ATPase in the refilling of thapsigargin- and agonist-mobilized Ca(2+) stores.
Our objective was to evaluate the role of vacuolar H(+)-ATPase and proton gradients in the refilling of Ca(2+) stores in fura-2-loaded pancreatic acinar cells. Once depleted with a high level of ACh, the Ca(2+) stores were replenished with a Ca(2+)-containing solution. The degree of refilling was estimated with a second release in response to either ACh (ACh-releasable store) or thapsigargin (thapsigargin-releasable store), a specific inhibitor of the endoplasmic reticulum Ca(2+) pumps. Both the protonophore nigericin and folimycin, a specific inhibitor of the vacuolar H(+)-ATPase, reduced reuptake into the ACh-mobilized stores but not into the thapsigargin-releasable pools. These treatments effectively dissipated the subcellular pH gradients (revealed by confocal observation of the distribution of a marker for acidic compartments), and did not impair the [Ca(2+)](i) response to ACh in control cells. Our results indicate that thapsigargin and ACh release heterogeneous Ca(2+) stores which are differently operated by vacuolar proton ATPase.
Camello-Almaraz
C
C
Department of Physiology, University of Extremadura, Cáceres, 10071, Spain.
Pariente
J A
JA
Salido
G
G
Camello
P J
PJ
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016257:Fura-2 / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007476:Ionophores / Q000494:pharmacology; D018942:Macrolides; D051379:Mice; D018613:Microscopy, Confocal; D009550:Nigericin / Q000494:pharmacology; D010179:Pancreas / Q000201:enzymology*; D006180:Proton-Translocating ATPases / Q000502:physiology*; D011522:Protons; D019284:Thapsigargin / Q000378:metabolism*; D013997:Time Factors; D014617:Vacuoles / Q000201:enzymology*
D000900:Anti-Bacterial Agents; D004791:Enzyme Inhibitors; D007476:Ionophores; D018942:Macrolides; D011522:Protons; D019284:Thapsigargin; C036978:concanamycin A; D006180:Proton-Translocating ATPases; D009550:Nigericin; D002118:Calcium; D016257:Fura-2