Ca(2+)-activated K+ channels in isolated type I cells of the neonatal rat carotid body.

Abstract

1. Ca(2+)-activated K+ (K+Ca) channels in neonatal rat type I carotid body cells were studied using single channel patch clamp techniques. In outside-out patches, using symmetrical 120 mM [K+] solutions, channels were observed with a slope conductance of 190 pS and a reversal potential of 0 mV. Reducing [K+]o to 5 mM shifted the reversal potential as expected for a K(+)-selective channel. 2. With 100 nM Ca2+ bathing the cytosolic aspect of patches, channel activity (number of active channels in a patch x open probability, NPo) increased with depolarization. NPo also increased with increasing 'cytosolic' [Ca2+] at a fixed membrane potential (0 mV). Using outside-out patches, bath application of 20 or 100 nM charybdotoxin reduced NPo by > 85%. These data indicate the presence of K+Ca channels in type I cells. 3. At 0 mV, using solutions of identical composition (1 microM Ca2+ bathing the cytosolic aspect of the channels), NPo was higher in outside-out patches than in inside-out patches. NPo was greatest in recordings using the perforated-vesicle technique. 4. Hypoxia and anoxia were without effect on K+Ca channels in outside-out patches, but caused significant, reversible reductions of NPo in channels recorded in perforated vesicles. 5. The whole-cell perforated-patch technique was used to record membrane potential at 35-37 degrees C. Hypoxia, anoxia and charybdotoxin all depolarized type I cells. 6. Our results suggest an important role for K+Ca channels in type I carotid body cells, and their activity in relation to a model for chemotransduction is discussed.

• Authors: C N Wyatt, C Peers
• Journal: The Journal of physiology (J Physiol) Vol. 483 ( Pt 3) Pg. 559-65 (Mar 15 1995) ISSN: 0022-3751 [Print] England
• PMID: 7539843 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Potassium Channels
• Scorpion Venoms
• Charybdotoxin
• Oxygen
• Calcium

Topics

• Animals
• Animals, Newborn
• Calcium (pharmacology)
• Carotid Body (cytology, metabolism, physiology)
• Cell Separation
• Charybdotoxin
• Hypoxia (physiopathology)
• Membrane Potentials (drug effects)
• Oxygen (metabolism)
• Partial Pressure
• Potassium Channels (drug effects)
• Rats
• Scorpion Venoms (pharmacology)