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Calcium-activated potassium channels in canine airway smooth muscle
Journal article   Peer reviewed

Calcium-activated potassium channels in canine airway smooth muscle

John D McCann and Michael J Welsh
The Journal of physiology, Vol.372(1), pp.113-127
1986
DOI: 10.1113/jphysiol.1986.sp016000
PMCID: PMC1192754
PMID: 2425082
url
https://www.ncbi.nlm.nih.gov/pmc/articles/1192754View
Open Access

Abstract

Airway smooth muscle cells from canine trachealis muscle were dispersed by treatment with collagenase and elastase. Cells were identified as smooth muscle by their binding of anti-smooth muscle gamma-isoactin monoclonal antibodies and by their contraction in response to acetylcholine. The patch-clamp technique was used to study single channel currents in cell-attached and isolated patches of membrane. The most common single channel currents had a conductance of 266 +/- 12 pS (mean +/- S.D., n = 7) in symmetrical 135 mM-K solutions. The reversal potential of the channel was unaltered by large chemical gradients for Cl, Na and Ca and was determined exclusively by the chemical K gradient. Thus, the channel is highly selective for K. In both cell-attached and isolated patches of membrane, depolarization increased the frequency of channel opening and the duration of the open state. In isolated patches of membrane, increasing [Ca] on the cytoplasmic side of the membrane from 10(-8) to 10(-6) M increased both the frequency of channel opening and the duration of the open state. Tetraethylammonium, tetramethylammonium, or Cs (10 mM) on the cytoplasmic side of the membrane caused a voltage-dependent decrease in conductance of the open channel while having no obvious effect on channel kinetics. These blocks were completely reversible. Ba (10 mM) on the cytoplasmic side of the membrane slightly decreased inward currents and completely blocked outward currents through the channel. External Ba (10 mM) caused a voltage-dependent decrease in inward current. External tetraethylammonium (10 mM) completely blocked single channel currents.
 Fundamental and applied biological sciences. Psychology Biological and medical sciences Air breathing Vertebrates: respiratory system Respiratory system: anatomy, metabolism, gas exchange, ventilatory mechanics, respiratory hemodynamics

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