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Biochem J. Jun 1, 1997; 324(Pt 2): 645–651.
PMCID: PMC1218477

Phospholipase C inhibitor, U73122, releases intracellular Ca2+, potentiates Ins(1,4,5)P3-mediated Ca2+ release and directly activates ion channels in mouse pancreatic acinar cells.


It is recognized in many cellular systems that the receptor/G-protein activation of phospholipase C and Ins(1,4,5)P3 production is the transduction pathway regulating the release of Ca2+ from internal stores. Ca2+ signals can now be monitored at the level of single cells but the biochemical detection of Ins(1,4,5)P3 cannot match this resolution. It is often difficult or impossible to directly attribute responses evoked in single cells by putative phospholipase C-coupled agonists to changes in Ins(1,4,5)P3 levels. U73122 is an aminosteroid that is reported to act as a specific inhibitor of phospholipase C and it has become an important tool in establishing the link between phospholipase C activation and cellular Ca2+ signalling. In the present study we use both patch-clamp electrophysiology and the imaging of fluorescent Ca2+ indicators to investigate the effect of U73122 in mouse pancreatic acinar cells. The study reveals that U73122 has effects other than the inhibition of phospholipase C. U73122 can directly activate ion channels. It can itself promote the release of Ca2+ from intracellular stores in permeabilized cells and in intact cells it triggers a release of Ca2+ that is initiated specifically at the secretory pole of these morphologically and functionally polarized cells. We also present evidence that U73122 can potentiate the response to Ins(1,4,5)P3; this is seen both in permeabilized cells and in patch-clamp protocols in which cells are internally dialysed with submaximal concentrations of Ins(1,4,5)P3. The effects of U73122 are therefore multiple and not specific for the inhibition of phospholipase C. Importantly, all the effects described influence Ca2+ signalling yet in many experimental protocols some of these effects can go unnoticed and might in error be attributed simply to the inhibition of Ins(1,4,5)P3 production.

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Selected References

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  • Berridge MJ. Inositol trisphosphate and calcium signalling. Nature. 1993 Jan 28;361(6410):315–325. [PubMed]
  • Rooney TA, Renard DC, Sass EJ, Thomas AP. Oscillatory cytosolic calcium waves independent of stimulated inositol 1,4,5-trisphosphate formation in hepatocytes. J Biol Chem. 1991 Jul 5;266(19):12272–12282. [PubMed]
  • Lawrie AM, Toescu EC, Gallacher DV. Two different spatiotemporal patterns for Ca2+ oscillations in pancreatic acinar cells: evidence of a role for protein kinase C in Ins(1,4,5)P3-mediated Ca2+ signalling. Cell Calcium. 1993 Nov;14(10):698–710. [PubMed]
  • Yule DI, Essington TE, Williams JA. Pilocarpine and carbachol exhibit markedly different patterns of Ca2+ signaling in rat pancreatic acinar cells. Am J Physiol. 1993 Apr;264(4 Pt 1):G786–G791. [PubMed]
  • Matozaki T, Göke B, Tsunoda Y, Rodriguez M, Martinez J, Williams JA. Two functionally distinct cholecystokinin receptors show different modes of action on Ca2+ mobilization and phospholipid hydrolysis in isolated rat pancreatic acini. Studies using a new cholecystokinin analog, JMV-180. J Biol Chem. 1990 Apr 15;265(11):6247–6254. [PubMed]
  • Saluja AK, Dawra RK, Lerch MM, Steer ML. CCK-JMV-180, an analog of cholecystokinin, releases intracellular calcium from an inositol trisphosphate-independent pool in rat pancreatic acini. J Biol Chem. 1992 Jun 5;267(16):11202–11207. [PubMed]
  • Bleasdale JE, Thakur NR, Gremban RS, Bundy GL, Fitzpatrick FA, Smith RJ, Bunting S. Selective inhibition of receptor-coupled phospholipase C-dependent processes in human platelets and polymorphonuclear neutrophils. J Pharmacol Exp Ther. 1990 Nov;255(2):756–768. [PubMed]
  • Smith RJ, Sam LM, Justen JM, Bundy GL, Bala GA, Bleasdale JE. Receptor-coupled signal transduction in human polymorphonuclear neutrophils: effects of a novel inhibitor of phospholipase C-dependent processes on cell responsiveness. J Pharmacol Exp Ther. 1990 May;253(2):688–697. [PubMed]
  • Yule DI, Williams JA. U73122 inhibits Ca2+ oscillations in response to cholecystokinin and carbachol but not to JMV-180 in rat pancreatic acinar cells. J Biol Chem. 1992 Jul 15;267(20):13830–13835. [PubMed]
  • Willems PH, Van de Put FH, Engbersen R, Bosch RR, Van Hoof HJ, de Pont JJ. Induction of Ca2+ oscillations by selective, U73122-mediated, depletion of inositol-trisphosphate-sensitive Ca2+ stores in rabbit pancreatic acinar cells. Pflugers Arch. 1994 Jun;427(3-4):233–243. [PubMed]
  • Wakui M, Potter BV, Petersen OH. Pulsatile intracellular calcium release does not depend on fluctuations in inositol trisphosphate concentration. Nature. 1989 May 25;339(6222):317–320. [PubMed]
  • Petersen CC, Toescu EC, Potter BV, Petersen OH. Inositol triphosphate produces different patterns of cytoplasmic Ca2+ spiking depending on its concentration. FEBS Lett. 1991 Nov 18;293(1-2):179–182. [PubMed]
  • Thorn P, Lawrie AM, Smith PM, Gallacher DV, Petersen OH. Local and global cytosolic Ca2+ oscillations in exocrine cells evoked by agonists and inositol trisphosphate. Cell. 1993 Aug 27;74(4):661–668. [PubMed]
  • Fabiato A, Fabiato F. Contractions induced by a calcium-triggered release of calcium from the sarcoplasmic reticulum of single skinned cardiac cells. J Physiol. 1975 Aug;249(3):469–495. [PMC free article] [PubMed]
  • Grynkiewicz G, Poenie M, Tsien RY. A new generation of Ca2+ indicators with greatly improved fluorescence properties. J Biol Chem. 1985 Mar 25;260(6):3440–3450. [PubMed]
  • Yule DI, Gallacher DV. Oscillations of cytosolic calcium in single pancreatic acinar cells stimulated by acetylcholine. FEBS Lett. 1988 Nov 7;239(2):358–362. [PubMed]
  • Osipchuk YV, Wakui M, Yule DI, Gallacher DV, Petersen OH. Cytoplasmic Ca2+ oscillations evoked by receptor stimulation, G-protein activation, internal application of inositol trisphosphate or Ca2+: simultaneous microfluorimetry and Ca2+ dependent Cl- current recording in single pancreatic acinar cells. EMBO J. 1990 Mar;9(3):697–704. [PMC free article] [PubMed]
  • Petersen OH, Gallacher DV. Electrophysiology of pancreatic and salivary acinar cells. Annu Rev Physiol. 1988;50:65–80. [PubMed]
  • Missiaen L, Taylor CW, Berridge MJ. Spontaneous calcium release from inositol trisphosphate-sensitive calcium stores. Nature. 1991 Jul 18;352(6332):241–244. [PubMed]
  • Thorn P, Brady P, Llopis J, Gallacher DV, Petersen OH. Cytosolic Ca2+ spikes evoked by the thiol reagent thimerosal in both intact and internally perfused single pancreatic acinar cells. Pflugers Arch. 1992 Nov;422(2):173–178. [PubMed]
  • Toescu EC, Lawrie AM, Petersen OH, Gallacher DV. Spatial and temporal distribution of agonist-evoked cytoplasmic Ca2+ signals in exocrine acinar cells analysed by digital image microscopy. EMBO J. 1992 Apr;11(4):1623–1629. [PMC free article] [PubMed]
  • De Moel MP, Van de Put FH, Vermegen TM, De Pont JH, Willems PH. Effect of the aminosteroid, U73122, on Ca2+ uptake and release properties of rat liver microsomes. Eur J Biochem. 1995 Dec 1;234(2):626–631. [PubMed]

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