Secretory state regulates Zn2+ transport in gastric parietal cell of the rabbit

Am J Physiol Cell Physiol. 2009 Oct;297(4):C979-89. doi: 10.1152/ajpcell.00577.2008. Epub 2009 Aug 12.

Abstract

Secretory compartments of neurons, endocrine cells, and exocrine glands are acidic and contain high levels of labile Zn2+. Previously, we reported evidence that acidity is regulated, in part, by the content of Zn2+ in the secretory [i.e., tubulovesicle (TV)] compartment of the acid-secreting gastric parietal cell. Here we report studies focusing on the mechanisms of Zn2+ transport by the TV compartment in the mammalian (rabbit) gastric parietal cell. Uptake of Zn2+ by isolated TV structures was monitored with a novel application of the fluorescent Zn2+ reporter N-(6-methoxy-8-quinolyl)-para-toluenesulfonamide (TSQ). Uptake was suppressed by removal of external ATP or blockade of H+-K+-ATPase that mediates luminal acid secretion. Uptake was diminished with dissipation of the proton gradient across the TV membrane, suggesting Zn2+/H+ antiport as the connection between Zn2+ uptake and acidity in the TV lumen. In isolated gastric glands loaded with the reporter fluozin-3, inhibition of H+-K+-ATPase arrested the flow of Zn(2+) from the cytoplasm to the TV compartment and secretory stimulation with forskolin enhanced vectorial movement of cytoplasmic Zn2+ into the tubulovesicle/lumen (TV/L) compartment. Our findings suggest that Zn2+ accumulation in the TV/L compartment is physiologically coupled to secretion of acid. These findings offer novel insight into mechanisms regulating Zn2+ homeostasis in the gastric parietal cell and potentially other cells in which acidic subcellular compartments serve signature functional roles.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aminoquinolines
  • Animals
  • Cations, Divalent / metabolism
  • Fluorescent Dyes
  • H(+)-K(+)-Exchanging ATPase / metabolism*
  • Hydrogen-Ion Concentration
  • In Vitro Techniques
  • Ion Transport
  • Parietal Cells, Gastric / metabolism*
  • Rabbits
  • Tosyl Compounds

Substances

  • Aminoquinolines
  • Cations, Divalent
  • Fluorescent Dyes
  • Tosyl Compounds
  • N-(6-methoxy-8-quinolyl)-4-toluenesulfonamide
  • H(+)-K(+)-Exchanging ATPase