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Potassium channel activators and bronchial asthma.
Summary
Cromakalim-like compounds relax airway smooth muscle by opening potassium channels. These compounds also reduce nerve activity in the lungs, potentially treating asthma by targeting airway hyper-reactivity.
Area of Science:
- Pharmacology
- Respiratory Medicine
- Cell Physiology
Background:
- Cromakalim-like compounds (KCOs) are known to relax airway smooth muscle.
- This relaxation is linked to the opening of plasmalemmal K(+)-channels, potentially similar to ATP-sensitive K(+)-channels.
Purpose of the Study:
- To investigate the mechanism of action of cromakalim-like KCOs on airway smooth muscle.
- To explore their bronchodilator activity and effects on neuroeffector transmission in the lung.
- To determine if KCOs alleviate nocturnal asthma through direct muscle relaxation or by inhibiting airway hyper-reactivity.
Main Methods:
- Electrophysiological studies on airway smooth muscle cells.
- In vivo assessment of bronchodilator activity.
- Investigation of effects on non-adrenergic, non-cholinergic (NANC) excitatory neuroeffector transmission.
Main Results:
- KCOs induce airway smooth muscle relaxation via plasmalemmal K(+)-channel opening.
- This K(+)-channel is likely not involved in normal airway smooth muscle membrane potential.
- KCOs exhibit bronchodilator activity and inhibit NANC transmission at lower concentrations than required for muscle relaxation.
Conclusions:
- KCOs relax airway smooth muscle through K(+)-channel opening, potentially via mechanisms beyond L-type voltage-operated calcium channel inhibition.
- KCOs possess in vivo bronchodilator effects and can modulate airway neuroeffector transmission.
- The therapeutic effect of cromakalim in nocturnal asthma may stem from inhibiting airway hyper-reactivity rather than direct smooth muscle relaxation.