Outward potassium current oscillations in macrophage polykaryons: extracellular calcium entry and calcium-induced calcium release
Outward current oscillations associated with transient membrane hyperpolarizations were induced in murine macrophage polykaryons by membrane depolarization in the absence of external Na+. Oscillations corresponded to a cyclic activation of Ca2+-dependent K+ currents (IKCa) probably correlated with v...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Associação Brasileira de Divulgação Científica
1997-01-01
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| Series: | Brazilian Journal of Medical and Biological Research |
| Subjects: | |
| Online Access: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X1997001100015 |
| _version_ | 1818766534291488768 |
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| author | Saraiva R.M. Masuda M.O. Oliveira-Castro G.M. |
| author_facet | Saraiva R.M. Masuda M.O. Oliveira-Castro G.M. |
| author_sort | Saraiva R.M. |
| collection | DOAJ |
| description | Outward current oscillations associated with transient membrane hyperpolarizations were induced in murine macrophage polykaryons by membrane depolarization in the absence of external Na+. Oscillations corresponded to a cyclic activation of Ca2+-dependent K+ currents (IKCa) probably correlated with variations in intracellular Ca2+ concentration. Addition of external Na+ (8 mM) immediately abolished the outward current oscillations, suggesting that the absence of the cation is necessary not only for their induction but also for their maintenance. Oscillations were completely blocked by nisoldipine. Ruthenium red and ryanodine reduced the number of outward current cycles in each episode, whereas quercetin prolonged the hyperpolarization 2- to 15-fold. Neither low molecular weight heparin nor the absence of a Na+ gradient across the membrane had any influence on oscillations. The evidence suggests that Ca2+ entry through a pathway sensitive to Ca2+ channel blockers is elicited by membrane depolarization in Na+-free medium and is essential to initiate oscillations, which are also dependent on the cyclic release of Ca2+ from intracellular Ca2+-sensitive stores; Ca2+ ATPase acts by reducing intracellular Ca2+, thus allowing slow deactivation of IKCa. Evidence is presented that neither a Na+/Ca2+ antiporter nor Ca2+ release from IP3-sensitive Ca2+ stores participate directly in the mechanism of oscillation |
| first_indexed | 2024-12-18T08:35:31Z |
| format | Article |
| id | doaj.art-0b1b7f69c4eb48358cef8d796da73275 |
| institution | Directory Open Access Journal |
| issn | 0100-879X 0034-7310 |
| language | English |
| last_indexed | 2024-12-18T08:35:31Z |
| publishDate | 1997-01-01 |
| publisher | Associação Brasileira de Divulgação Científica |
| record_format | Article |
| series | Brazilian Journal of Medical and Biological Research |
| spelling | doaj.art-0b1b7f69c4eb48358cef8d796da732752022-12-21T21:14:20ZengAssociação Brasileira de Divulgação CientíficaBrazilian Journal of Medical and Biological Research0100-879X0034-73101997-01-01301113491357Outward potassium current oscillations in macrophage polykaryons: extracellular calcium entry and calcium-induced calcium releaseSaraiva R.M.Masuda M.O.Oliveira-Castro G.M.Outward current oscillations associated with transient membrane hyperpolarizations were induced in murine macrophage polykaryons by membrane depolarization in the absence of external Na+. Oscillations corresponded to a cyclic activation of Ca2+-dependent K+ currents (IKCa) probably correlated with variations in intracellular Ca2+ concentration. Addition of external Na+ (8 mM) immediately abolished the outward current oscillations, suggesting that the absence of the cation is necessary not only for their induction but also for their maintenance. Oscillations were completely blocked by nisoldipine. Ruthenium red and ryanodine reduced the number of outward current cycles in each episode, whereas quercetin prolonged the hyperpolarization 2- to 15-fold. Neither low molecular weight heparin nor the absence of a Na+ gradient across the membrane had any influence on oscillations. The evidence suggests that Ca2+ entry through a pathway sensitive to Ca2+ channel blockers is elicited by membrane depolarization in Na+-free medium and is essential to initiate oscillations, which are also dependent on the cyclic release of Ca2+ from intracellular Ca2+-sensitive stores; Ca2+ ATPase acts by reducing intracellular Ca2+, thus allowing slow deactivation of IKCa. Evidence is presented that neither a Na+/Ca2+ antiporter nor Ca2+ release from IP3-sensitive Ca2+ stores participate directly in the mechanism of oscillationhttp://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X1997001100015macrophagemacrophage polykaryonCa2+-dependent K+ currentmembrane potential oscillationscalcium-induced calcium releaseCa2+ ATPase |
| spellingShingle | Saraiva R.M. Masuda M.O. Oliveira-Castro G.M. Outward potassium current oscillations in macrophage polykaryons: extracellular calcium entry and calcium-induced calcium release Brazilian Journal of Medical and Biological Research macrophage macrophage polykaryon Ca2+-dependent K+ current membrane potential oscillations calcium-induced calcium release Ca2+ ATPase |
| title | Outward potassium current oscillations in macrophage polykaryons: extracellular calcium entry and calcium-induced calcium release |
| title_full | Outward potassium current oscillations in macrophage polykaryons: extracellular calcium entry and calcium-induced calcium release |
| title_fullStr | Outward potassium current oscillations in macrophage polykaryons: extracellular calcium entry and calcium-induced calcium release |
| title_full_unstemmed | Outward potassium current oscillations in macrophage polykaryons: extracellular calcium entry and calcium-induced calcium release |
| title_short | Outward potassium current oscillations in macrophage polykaryons: extracellular calcium entry and calcium-induced calcium release |
| title_sort | outward potassium current oscillations in macrophage polykaryons extracellular calcium entry and calcium induced calcium release |
| topic | macrophage macrophage polykaryon Ca2+-dependent K+ current membrane potential oscillations calcium-induced calcium release Ca2+ ATPase |
| url | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X1997001100015 |
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