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Transmitter-induced changes of the membrane voltage of HT29 cells
E Lohrmann1, Z I Cabantchik, R Greger
1Physiologisches Institut der Albert-Ludwigs-Universität Freiburg, Federal Republic of Germany.
Abstract:
The colonic carcinoma cell line HT29 was used to examine the influence of agonists increasing cytosolic cAMP and Ca2+ activity on the conductances and the cell membrane voltage (Vm). HT29 cells were grown on glass cover-slips. Cells were impaled by microelectrodes 4-10 days after seeding, when they had formed large plaques. In 181 impalements Vm was -51 +/- 1 mV. An increase in bath K+ concentration from 3.6 mmol/l to 18.6 mmol/l or 0.5 mmol/l Ba2+ depolarized the cells by 10 +/- 1 mV (n = 49) or by 9 +/- 2 mV (n = 3), respectively. A decrease of bath Cl- concentration from 145 to 30 mmol/l depolarized the cells by 11 +/- 1 mV (n = 24). Agents increasing intracellular cAMP such as isobutylmethylxanthine (0.1 mmol/l), forskolin (10 mumol/l) or isoprenaline (10 mumol/l) depolarized the cells by 6 +/- 1 (n = 13), 15 +/- 3 (n = 5) and 6 +/- 2 (n = 3) mV, respectively. In hypoosmolar solutions (225 mosmol/l) cells depolarized by 9 +/- 1 mV (n = 6). Purine and pyrimidine nucleotides depolarized the cells dose-dependently with the following potency sequence: UTP greater than ATP greater than ITP greater than GTP greater than TTP greater than CTP = 0. The depolarization by ATP was stronger than that by ADP and adenosine. The muscarinic agonist carbachol led to a sustained depolarization by 27 +/- 6 mV (n = 5) at 0.1 mmol/l, and to a transient depolarization by 12 +/- 4 mV (n = 5) at 10 mumol/l. Neurotensin depolarized with a half-maximal effect at around 5 nmol/l.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
This study investigated how various substances affect the membrane voltage of HT29 colon cancer cells. Key findings show that cAMP-increasing agents and nucleotides depolarize these cells, impacting cell function.
Area of Science:
- Cellular Electrophysiology
- Colorectal Cancer Research
Background:
- The HT29 colon carcinoma cell line is a model for studying cellular responses.
- Understanding ion channel activity and membrane potential is crucial for cancer cell biology.
Purpose of the Study:
- To investigate the effects of agonists that increase cytosolic cyclic adenosine monophosphate (cAMP) and calcium (Ca2+) activity on HT29 cell membrane voltage (Vm).
- To characterize the changes in membrane potential induced by various signaling molecules.
Main Methods:
- Utilized microelectrode impalement to measure the membrane voltage (Vm) of HT29 cells grown on glass coverslips.
- Applied various ionic solutions (varying K+, Cl-, osmolarity) and agonists (cAMP inducers, nucleotides, carbachol, neurotensin) to assess their impact on Vm.
Main Results:
- Increased extracellular K+ or Ba2+ caused depolarization. Decreased extracellular Cl- also led to depolarization.
- Agents that increase intracellular cAMP, such as forskolin and isobutylmethylxanthine, depolarized the cells.
- Purine and pyrimidine nucleotides, particularly UTP and ATP, dose-dependently depolarized HT29 cells. Carbachol and neurotensin also induced significant depolarization.
Conclusions:
- Various signaling pathways involving cAMP, Ca2+, and specific agonists modulate the membrane potential of HT29 colon cancer cells.
- These findings provide insights into the electrophysiological properties of colon cancer cells and potential therapeutic targets.
