Responses to reversible anoxia of intracellular free and bound Ca(2+) in rat cortical slices.
Severe anoxia induces destabilisation of intracellular calcium homeostasis in neurones. The mechanism of this effect, and particularly the interrelationship between changes in intracellular concentration of free Ca(2+) ions and the content of the intracellular Ca(2+) stores, during and after anoxia, is not clear. We used a superfusion system of rat olfactory cortical slices for the fluorimetric estimation of changes in the intracellular concentration of free Ca(2+) ions and in the level of bound Ca(2+), utilising the fluorescent indicators Fura-2 and chlortetracycline, respectively. It was found that 10-min normoglycaemic anoxia results in simultaneous decrease in bound and increase in free Ca(2+) levels, whereas during 60-min reoxygenation, we detected an increase in both indices. The NMDA receptor antagonists MK-801 and APV attenuated changes in free Ca(2+) level during anoxia and reoxygenation and intensified anoxia-evoked decrease in bound Ca(2+) content, whereas a late post-anoxic increase in bound Ca(2+) was abolished. These data suggest that the influx of extracellular Ca(2+) to neurones via NMDA receptors, plays a critical role in the rise of intracellular free Ca(2+) concentration during and after anoxia. Biphasic changes in bound Ca(2+) content during anoxia and reoxygenation may reflect an anoxia-induced release of Ca(2+) from intracellular stores, followed later by a neuronal calcium overload and refilling of intracellular Ca(2+) binding sites.
Semenov
D G
DG
Pavlov Institute of Physiology, Russian Academy of Sciences, nab. Makarova 6, 199034, St. Petersburg, Russia.
Samoilov
M O
MO
Zielonka
P
P
Lazarewicz
J W
JW
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002751:Chlortetracycline; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2; D000860:Hypoxia / Q000378:metabolism*; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism*; D009833:Olfactory Pathways / Q000378:metabolism*; D010100:Oxygen / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D013997:Time Factors
D018691:Excitatory Amino Acid Antagonists; D005456:Fluorescent Dyes; D016194:Receptors, N-Methyl-D-Aspartate; D016291:Dizocilpine Maleate; D015763:2-Amino-5-phosphonovalerate; D010100:Oxygen; D002118:Calcium; D016257:Fura-2; D002751:Chlortetracycline