O2-sensitive K+ currents in carotid body chemoreceptor cells from normoxic and chronically hypoxic rats and their roles in hypoxic chemotransduction.

Abstract

Carotid body-mediated ventilatory increases in response to acute hypoxia are attenuated in animals reared in an hypoxic environment. Normally, O2-sensitive K+ channels in neurosecretory type I carotid body cells are intimately involved in excitation of the intact organ by hypoxia. We have therefore studied K+ channels and their sensitivity to acute hypoxia (PO2 12-20 mmHg) in type I cells isolated from neonatal rats born and reared in normoxic and hypoxic environments. When compared with cells from normoxic rats, K+ current density in cells from hypoxic rats was significantly reduced, whereas Ca2+ current density was unaffected. Charybdotoxin (20 nM) inhibited K+ currents in cells from normoxic rats by approximately 25% but was without significant effect in cells from hypoxic rats. However, hypoxia caused similar, reversible inhibitions of K+ currents in cells from the two groups. Resting membrane potentials (measured at 37 degrees C using the perforated-patch technique) were similar in normoxic and hypoxic rats. However, although acute hypoxia depolarized type I cells of normoxic rats, it was without effect on membrane potential in type I cells from hypoxic animals. Charybdotoxin (20 nM) also depolarized cells from normoxic rats. Our results suggest that type I cells from chronically hypoxic rats, like normoxic rats, possess O2-sensing mechanisms. However, they lack charybdotoxin-sensitive K+ channels that contribute to resting membrane potential in normoxically reared rats, and this appears to prevent them from depolarizing (and hence triggering Ca2+ influx and neurosecretion) during acute hypoxia.

• Authors: C N Wyatt, C Wright, D Bee, C Peers
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 92 Issue 1 Pg. 295-9 (Jan 03 1995) ISSN: 0027-8424 [Print] United States
• PMID: 7529413 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

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

Topics

• Animals
• Animals, Newborn
• Calcium Channels (drug effects, physiology)
• Carotid Body (physiology, physiopathology)
• Cells, Cultured
• Charybdotoxin
• Chemoreceptor Cells (physiology)
• Hypoxia (physiopathology)
• Membrane Potentials (drug effects, physiology)
• Neurons (drug effects, physiology)
• Oxygen (pharmacology)
• Potassium Channels (drug effects, physiology)
• Rats
• Rats, Wistar
• Reference Values
• Scorpion Venoms (pharmacology)
• Signal Transduction