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Oscillations of cytosolic free calcium in bombesin-stimulated HIT-T15 cells

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Published in Cell Calcium. 1996, vol. 19, no. 6, p. 535-46
Abstract The mechanism underlying the generation of cytosolic free Ca2+ ([Ca2+]i) oscillations by bombesin, a receptor agonist activating phospholipase C, in insulin secreting HIT-T15 cells was investigated. At 25 microM, 61% of cells displayed [Ca2+]i oscillations with variable patterns. The bombesin-induced [Ca2+]i oscillations could last more than 1 h and glucose was required for maintaining these [Ca2+]i fluctuations. Bombesin-evoked [Ca2+]i oscillations were dependent on extracellular Ca2+ entry and were attenuated by membrane hyperpolarization or by L-type Ca2+ channel blockers. These [Ca2+]i oscillations were apparently not associated with fluctuations in plasma membrane Ca2+ permeability as monitored by the Mn2+ quenching technique. 2,5-di-(tert-butyl)-1,4-benzohydroquinone (tBuBHQ) and 4-chloro-m-cresol, which interfere with intracellular Ca2+ stores, respectively, by inhibiting Ca(2+)-ATPase of endoplasmic reticulum and by affecting Ca(2+)-induced Ca2+ release, disrupted bombesin-induced [Ca2+]i oscillations. 4-chloro-m-cresol raised [Ca2+]i by mobilizing an intracellular Ca2+ pool, an effect not altered by ryanodine. Caffeine exerted complex actions on [Ca2+]i. It raised [Ca2+]i by promoting Ca2+ entry while inhibiting bombesin-elicited [Ca2+]i oscillations. Our results suggest that in bombesin-elicited [Ca2+]i oscillations in HIT-T15 cells: (i) the oscillations originate primarily from intracellular Ca2+ stores; and (ii) the Ca2+ influx required for maintaining the oscillations is in part membrane potential-sensitive and not coordinated with [Ca2+]i oscillations. The interplay between intracellular Ca2+ stores and voltage-sensitive and voltage-insensitive extracellular Ca2+ entry determines the [Ca2+]i oscillations evoked by bombesin.
Keywords AnimalsBiological Clocks/drug effects/physiologyBombesin/pharmacologyCaffeine/pharmacologyCalcium/analysis/metabolismCalcium Channel Blockers/pharmacologyCalcium Channels/drug effects/metabolismCalcium-Transporting ATPases/antagonists & inhibitorsCell LineCentral Nervous System Stimulants/pharmacologyChelating Agents/pharmacologyCircadian RhythmCresols/pharmacologyCricetinaeCytosol/drug effects/metabolismDiazoxide/pharmacologyEgtazic Acid/pharmacologyFura-2/pharmacologyGlucose/pharmacologyHydroquinones/pharmacologyMembrane Potentials/drug effectsRyanodine/pharmacologyVerapamil/pharmacology
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PMID: 8842521
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LI, Guodong, WOLLHEIM, Claes, PRALONG, William. Oscillations of cytosolic free calcium in bombesin-stimulated HIT-T15 cells. In: Cell Calcium, 1996, vol. 19, n° 6, p. 535-46. https://archive-ouverte.unige.ch/unige:35655

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