Details

Autor(en) / Beteiligte

• De Pascual, Ricardo
• Colmena, Ines
• Ruiz-Pascual, Lucia
• Baraibar, Andres Mateo
• Egea, Javier
• Gandia, Luis
• Garcia, Antonio G

Titel

Regulation by L channels of Ca super(2+)-evoked secretory responses in ouabain-treated chromaffin cells

Ist Teil von

• Pflügers Archiv, 2016-10, Vol.468 (10), p.1779-1792

Erscheinungsjahr

2016

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• It is known that the sustained depolarisation of adrenal medullary bovine chromaffin cells (BCCs) with high K super(+) concentrations produces an initial sharp catecholamine release that subsequently fades off in spite depolarisation persists. Here, we have recreated a sustained depolarisation condition of BCCs by treating them with the Na super(+)/K super(+) ATPase blocker ouabain; in doing so, we searched experimental conditions that permitted the development of a sustained long-term catecholamine release response that could be relevant during prolonged stress. BCCs were perifused with nominal 0Ca super(2+) solution, and secretion responses were elicited by intermittent application of short 2Ca super(2+) pulses (Krebs-HEPES containing 2 mM Ca super(2+)). These pulses elicited a biphasic secretory pattern with an initial 30-min period with secretory responses of increasing amplitude and a second 30-min period with steady-state, non-inactivating responses. The initial phase was not due to gradual depolarisation neither to gradual increases of the cytosolic calcium transients ([Ca super(2+)] sub(c)) elicited by 2Ca super(2+) pulses in BBCs exposed to ouabain; both parameters increased soon after ouabain addition. Iifedipine blocked these responses, and FPL64176 potentiated them, suggesting that they were triggered by Ca super(2+) entry through non-inactivating L-type calcium channels. This was corroborated by nifedipine-evoked blockade of the L-type Ca super(2+) channel current and the [Ca super(2+)] sub(c) transients elicited by 2Ca super(2+) pulses. Furthermore, the plasmalemmal Na super(+)/Ca super(2+) exchanger (NCX) blocker SEA0400 caused a mild inhibition followed by a large rebound increase of the steady-state secretory responses. We conclude that these two phases of secretion are mostly contributed by Ca super(2+) entry through L calcium channels, with a minor contribution of Ca super(2+) entry through the reverse mode of the NCX.