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 language | English (US) |
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Pages (from-to) | G92-G103 |
Journal | American Journal of Physiology - Gastrointestinal and Liver Physiology |
Volume | 261 |
Issue number | 1 24-1 |
DOIs | |
State | Published - 1991 |
Externally published | Yes |
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)