Responses to reversible anoxia of intracellular free and bound Ca(2+) in rat cortical slices

• Published in: Resuscitation 2000-05, Vol.44 (3), p.207-214
• Main Authors: Semenov, D G, Samoilov, M O, Zielonka, P, Lazarewicz, J W
• Format: Article
• Language: English
• Subjects: 2-Amino-5-phosphonovalerate - pharmacology; Animals; Calcium - metabolism; Chlortetracycline; Dizocilpine Maleate - pharmacology; Excitatory Amino Acid Antagonists - pharmacology; Fluorescent Dyes; Fura-2; Hypoxia - metabolism; In Vitro Techniques; Intracellular Membranes - metabolism; Olfactory Pathways - metabolism; Oxygen - pharmacology; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate - physiology; Time Factors
• ISSN: 0300-9572
• DOI: 10.1016/S0300-9572(00)00136-2

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.