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Atrial natriuretic polypeptide hormones induce membrane potential responses in cultured rat glioma cells
Abstract:
Atrial natriuretic hormones (ANHs) applied to polyploid rat glioma cells induced hyperpolarizations of about 30 s duration, followed by depolarizations lasting 1-2 min. Repeated applications of the peptide resulted in desensitization. The reversal potential of -87 mV at an extracellular K+ concentration of 5 mM and the decrease of membrane resistance during the hyperpolarization indicate that K+ channels were activated by ANH. In these cells the fluorescence signal of 2-[(2-bis[carboxymethyl]amino-5-methylphenoxy)-methyl]-6-methoxy-8-bis [carboxymethyl]aminoquinoline (quin2) was not affected by ANH suggesting that ANH did not change the cytosolic Ca2+-activity.
Insights
Atrial natriuretic hormones (ANHs) activate potassium channels in rat glioma cells, causing electrical changes. ANHs did not affect intracellular calcium levels, indicating a specific ion channel mechanism.
Area of Science:
- Neuroscience
- Cell Biology
- Pharmacology
Background:
- Atrial natriuretic hormones (ANHs) are peptides with known physiological roles.
- Glioma cells, a type of brain tumor cell, are often studied for their electrophysiological properties.
Purpose of the Study:
- To investigate the effects of Atrial natriuretic hormones (ANHs) on the electrophysiological properties of polyploid rat glioma cells.
- To determine the specific ion channels involved in the cellular response to ANHs.
- To assess the impact of ANHs on intracellular calcium levels in these cells.
Main Methods:
- Application of ANHs to cultured polyploid rat glioma cells.
- Measurement of membrane potential and resistance using electrophysiological techniques.
- Determination of reversal potential at varying extracellular potassium concentrations.
- Monitoring of intracellular calcium activity using the fluorescent indicator quin2.
Main Results:
- ANH application induced transient hyperpolarizations followed by longer depolarizations in glioma cells.
- A reversal potential of -87 mV and decreased membrane resistance during hyperpolarization suggested K+ channel activation by ANH.
- Repeated ANH exposure led to cellular desensitization.
- ANH did not alter the fluorescence signal of quin2, indicating no change in cytosolic Ca2+-activity.
Conclusions:
- Atrial natriuretic hormones (ANHs) activate potassium channels in rat glioma cells, leading to significant changes in membrane potential.
- The observed effects are specific to K+ channel activation and do not involve alterations in cytosolic calcium concentration.
- These findings provide insights into the cellular mechanisms of ANH action in glioma cells.