Calcium regulated chloride permeabilities in primary cultures of rabbit colonocytes
J Sahi, MP Wiggins, GB Gibori… - Journal of cellular …, 1996 - Wiley Online Library
J Sahi, MP Wiggins, GB Gibori, TJ Layden, MC Rao
Journal of cellular physiology, 1996•Wiley Online LibraryTo determine if calcium‐dependent secretagogues directly act on epithelial cells to elicit CI−
secretion, their effects on CI− transport and intracellular Ca2+ concentrations ([Ca2+] i) were
determined in primary cultures of rabbit distal colonic crypt cells. The Cl− sensitive
fluorescent probe, 6‐methoxyquinolyl acetoethyl ester, MQAE and the Ca2+‐sensitive
fluorescent probe, fura‐2AM were used to assess Cl− transport and [Ca2+] i, respectively.
Basal Cl− transport (0.274±0.09 mM/sec) was inhibited significantly by the Cl− channel …
secretion, their effects on CI− transport and intracellular Ca2+ concentrations ([Ca2+] i) were
determined in primary cultures of rabbit distal colonic crypt cells. The Cl− sensitive
fluorescent probe, 6‐methoxyquinolyl acetoethyl ester, MQAE and the Ca2+‐sensitive
fluorescent probe, fura‐2AM were used to assess Cl− transport and [Ca2+] i, respectively.
Basal Cl− transport (0.274±0.09 mM/sec) was inhibited significantly by the Cl− channel …
Abstract
To determine if calcium‐dependent secretagogues directly act on epithelial cells to elicit CI− secretion, their effects on CI− transport and intracellular Ca2+ concentrations ([Ca2+]i) were determined in primary cultures of rabbit distal colonic crypt cells. The Cl− sensitive fluorescent probe, 6‐methoxyquinolyl acetoethyl ester, MQAE and the Ca2+‐sensitive fluorescent probe, fura‐2AM were used to assess Cl− transport and [Ca2+]i, respectively. Basal Cl− transport (0.274 ± 0.09 mM/sec) was inhibited significantly by the Cl− channel blocker diphenylamine‐2‐carboxylate (DPC, 50 μM, 0.068 ± 0.02 mM/sec; P < 0.001) and the Na+/K+/2Cl− cotransport inhibitor furosemide (1 μM, 0.137 ± 0.04 mM/sec; P < 0.01). Ion substitution studies using different halides revealed the basal influx to be I− > F− ≥ Cl− > Br−. DPC inhibited I− influx by ∼50%, F− influx by 80%, Cl− influx by 85%, and Br− influx by 90%. Furosemide significantly inhibited influx of Br− (84%) and Cl− (81%) but not of F− and I−. The effects of agents known to alter biological response by increasing [Ca2+]i in other epithelial systems were used to stimulate Cl− transport. Cl− influx in mM/second was stimulated by 1 μM histamine (0.58 ± 0.05), 10 μM neurotensin (2.07 ± 0.32), 1 μM serotonin (1.63 ± 0.28), and 0.1 μM of the Ca2+ ionophore A23187 (2.05 ± 0.40). The Cl− permeability stimulated by neurotensin, serotonin, and A23187 was partially blocked by DPC or furosemide added alone or in combination. Histamine‐induced Cl− influx was significantly inhibited by only furosemide. Indomethacin blocked histamine‐stimulated Cl− permeability but had no effect on the actions of the other agents. These studies, focusing on isolated colonocytes without the contribution of submucosal elements, reveal that (1) histamine stimulates Cl− transport by activating the Na+/K+/2Cl− cotransporter via a cyclooxygenase‐dependent pathway; (2) neurotensin, serotonin, and A23187 activate both Cl− channels and the cotransporter, and their actions are cyclooxygenase‐independent. © 1996 Wiley‐Liss, Inc.
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