AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 4 963-R969, Copyright © 1995 by American Physiological Society
Low-conductance anion channel activated by cAMP in teleost Cl- -secreting cells
W. S. Marshall, S. E. Bryson, A. Midelfart and W. F. Hamilton
Department of Biology, St. Francis Xavier University, Antigonish, Nova Scotia, Canada.
We studied characteristics and modulation of ion channels in primary
cultures of opercular epithelium from the euryhaline marine killifish
Fundulus heteroclitus. Primary cultures, 17-28 h old, retain
mitochondria-rich Cl- cells identifiable by fluorescence microscopy.
Cell-attached patches revealed frequent low-conductance 8.1 +/- 0.35 pS
channels that usually became inactive on excision; high-conductance anion
channels were not apparent. Ion substitution experiments demonstrated
selectivity for Cl- over gluconate of 1:0.07. With addition of
1-isobutyl-3-methylxanthine (0.1 mM) and dibutyryladenosine 3',5'-cyclic
monophosphate (1.0 mM) to the bath, incidence of the channel increased from
35.3 to 61.9% of total patches (n = 156 and 21, respectively), and
incidence of patches with multiple copies of the channel increased markedly
from 2.2 to 38.5%. Epithelial Cl- transport was inhibited by mucosally
added diphenylamine-2-carboxylic acid (1.0 mM) but not by
4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (0.1-1.0 mM). The anion
channel was absent from cultured killifish corneal epithelium, a tissue
that lacks Cl- cells. We conclude that a low-conductance anion channel of
Cl- cells, likely in the apical membrane, may account for adenosine
3',5'-cyclic monophosphate-activated Cl- secretion by marine fish.
