Low doses of ethanol have Ca2+ ionophore-like effects on apical membrane potential of in vitro Necturus antrum

M. J. Rutten, C. D. Moore

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

The effects of low doses of luminal ethanol on the amiloride-sensitive apical membrane potential of Necturus antral mucosa were studied using conventional microelectrode techniques. Luminal ethanol (0.250-4.0% vol/vol) caused a dose-dependent hyperpolarization of the apical membrane potential (V(mc)), an increase in transepithelial resistance (R(t)) and resistance ratio (R(a)/R(b)), and a decrease in transepithelial potential (V(ms)). Luminal amiloride (100 μM) to 4% ethanol-treated antra did not cause any additional hyperpolarization of V(mc). Compared with luminal 2% ethanol-Ringer, an equivalent osmotic mannitol solution depolarized V(mc) and basolateral potential (V(cs)), decreased R(t) and R(a)/R(b), and increased V(ms). A single dose of 0.50% ethanol attenuated the effects of a second 2% ethanol exposure on V(mc). No change in periodic acid-Schiff (PAS)-positive mucous granule content could be found between control and 2% ethanol-treated antra. The Ca2+ ionophores A23187 or ionomycin (0.25-5.0 μM) dose dependently hyperpolarized the V(mc) and V(cs), increased R(t) and R(a)/R(b), and decreased V(ms). Luminal Ca2+-free Ringer had no effect on luminal 2.00% ethanol-induced changes in membrane potentials or resistances. Pretreatment with BAPTA blocked by ~70 and 55% the V(mc) hyperpolarization of 2 and 4% ethanol, respectively. Pretreatment with ruthenium red (10-50 μM) also dose dependently reduced the 2% ethanol-induced changes in V(mc). The data indicate that 1) low doses of luminal ethanol and Ca2+ ionophores have similar effects on Necturus gastric antral membrane potentials and resistances, 2) ethanol-induced hyperpolarizations of the V(mc) are partially mediated through an alteration in intracellular Ca2+, and 3) low doses of luminal ethanol do not cause the release of antral epithelial mucous granules at the time when significant changes are occurring in the V(mc).

Original languageEnglish (US)
Pages (from-to)G92-G103
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume261
Issue number1 24-1
StatePublished - Jan 1 1991

    Fingerprint

Keywords

  • 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
  • A23187
  • Amiloride
  • Calcium permeability
  • Gastric antrum
  • Ionomycin
  • Mucus
  • Ruthenium red
  • Sodium permeability

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

Cite this