Premium
Anoxia‐mediated decrease in whole‐cell conductance and identification of putative background K+‐like currents in anoxia‐tolerant turtle liver
Author(s) -
Hogg David William,
Buck Leslie Thomas
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.1043.5
Subject(s) - painted turtle , depolarization , membrane potential , potassium channel , biophysics , ion channel , potassium , chemistry , patch clamp , anoxic waters , conductance , biochemistry , biology , receptor , turtle (robot) , mathematics , organic chemistry , combinatorics , fishery , environmental chemistry
To survive months of anoxia painted turtles ( Chrysemys picta bellii ) suppress ATP utilizing pathways, enabling metabolic demands to be met through anaerobic ATP production. Ion pumping is a major ATP utilizing pathway and a decrease in membrane permeability to ions or ion channel arrest (CA) is thought to reduce ATP demand. Evidence supporting CA in anoxic turtle brain includes a 50% decrease in both major excitatory glutamatergic receptor/channels ‐ AMPA and NMDA. Recently we have shown that a 25% increase in whole‐cell conductance (G w ) occurs and this is due to an increase in GABA‐A receptor currents that clamp resting membrane potential (MP) at a hyperpolarized state preventing action potential generation. In non‐excitable anoxic liver MP is maintained while Na + /K + ATPase activity decreases by 75%, indirectly providing evidence for CA. Using a liver slice model, we investigated anoxia‐mediated CA directly using whole‐cell and single‐channel electrophysiological techniques. We found anoxia induces a 16% depolarization of MP, 25 ± 5 mV to 21 ± 0.2mV and a 20 ± 3% decrease in G w . We also identified a 3–5 pA potassium current that was active at normoxic MP and upon anoxia activity decreased by 40%. We conclude that 1) in liver G w decreases with anoxia to reduce the ATP cost of maintaining concentration gradients, 2) anoxia modulates potassium currents with characteristics similar to background potassium channels.