Pulses of extracellular K+ produce two cytosolic Ca2+ transients that display different temperature dependence and carbonyl cyanide m -chlorophenyl sensitivity in SH-SY5Y cells

• Published in: Brain research 2008-06, Vol.1213, p.12-26
• Main Authors: Montoya G., José V, Sutachan, Jhon-Jairo, Corrales, Alexandra, Xu, Fang, Blanck, Thomas J.J, Recio-Pinto, Esperanza
• Format: Article
• Language: English
• Subjects: Anticonvulsants - pharmacology; Biological and medical sciences; Caffeine - pharmacology; Calcium - metabolism; Carbonyl Cyanide m-Chlorophenyl Hydrazone - pharmacology; Cell Line, Tumor; Cell physiology; Clonazepam - analogs & derivatives; Clonazepam - pharmacology; Cytosol - metabolism; Dose-Response Relationship, Drug; Drug Interactions; Extracellular Fluid - drug effects; Fundamental and applied biological sciences. Psychology; Humans; Ionophores - pharmacology; Membrane and intracellular transports; Molecular and cellular biology; Neuroblastoma - pathology; Neurology; Nitriles; Phosphodiesterase Inhibitors - pharmacology; Potassium Chloride - pharmacology; Temperature; Thiazepines - pharmacology; Time Factors
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2008.03.022

Abstract In SH-SY5Y cells we have shown that stimulation with high extracellular K+ ([K+ ]e ) evokes a transient increase in cytoplasmic Ca2+ ([Ca2+ ]cyt ) (K+on ) that is triggered by the opening of voltage-dependent Ca2+ channels and followed by Ca2+ -induced Ca2+ release from the endoplasmic reticulum (Xu, F., Zhang, J., Recio-Pinto, E. and Blanck, T.J., Halothane and isoflurane augment depolarization-induced cytosolic CA2+ transients and attenuate carbachol-stimulated CA2+ transients, Anesthesiology, 92 (2000) 1746–56). The removal of high-[K+ ]e results in a second transient increase in [Ca2+ ]cyt (K+off ) that is independent of extracellular Ca2+ (Corrales, A., Montoya, G.J., Sutachan, J.J., Cornillez-Ty, G., Garavito-Aguilar, Z., Xu, F., Blanck, T.J. and Recio-Pinto, E., Transient increases in extracellular K+ produce two pharmacological distinct cytosolic Ca2+ transients, Brain Res., 1031 (2005) 174–184). In this study we further characterize the properties of K+off . We found that K+off was detectable at near physiological temperatures (34–36 °C) but, depending on the level of [K+ ]e , it was undetectable or highly diminished at room temperature. In contrast, K+on was increased by lowering the temperature. Extracellular Na+ -replacement with K+ did not affect K+off , indicating that K+off was not generated by osmolarity changes. Replacement of extracellular Na+ with choline+ did not affect K+off , indicating that K+off did not result from activity changes of the plasma membrane Na+ /Ca2+ exchanger. Caffeine decreased K+on but not K+off . CCCP (carbonyl cyanide m -chlorophenyl), a protonophore uncoupler that decreases mitochondrial Ca2+ uptake, decreased K+on but not K+off . CGP37157, an inhibitor of the mitochondria Na+ /Ca2+ exchanger, decreased K+off when added alone but not when added simultaneously with CCCP. Clonazepam had similar effects as CGP37157. These findings indicate that the generation of K+off is strongly temperature-dependent and its pharmacology is distinct from the [Ca2+ ]cyt changes observed previously at room temperature.