Capacitative calcium entry in guinea pig gallbladder smooth muscle in vitro

Mechanism of a methylxanthine drug theophylline-induced Ca2+ signaling and cytotoxicity in AML12 mouse hepatocytes

Theophylline is a methylxanthine drug used in therapy for respiratory diseases. However, the impact of theophylline on Ca²⁺ signaling has not been explored in liver cells. This study examined whether theophylline affected Ca²⁺ homeostasis and its related cytotoxicity in AML12 mouse hepatocytes. Cell viability was measured by the cell viability reagent (WST-1). Cytosolic Ca²⁺ concentration ([Ca²⁺]_i) was measured by the Ca²⁺-sensitive fluorescent dye fura-2. Theophylline (25-125 μM) induced [Ca²⁺]_i rises and cause cytotoxicity in AML12 cells. This cytotoxic response was reversed by chelation of cytosolic Ca²⁺ with BAPTA/AM. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin abolished theophylline-induced [Ca²⁺]_i rises. Conversely, treatment with theophylline also abolished thapsigargin-induced [Ca²⁺]_i rises. However, inhibition of PLC failed to alter theophylline-evoked [Ca²⁺]_i rises. In Ca²⁺-containing medium, modulators of store-operated Ca²⁺ channels inhibited 30% of the [Ca²⁺]_i rises, whereas the PKC modulators had no effect. Furthermore, theophylline-induced Ca²⁺ influx was confirmed by Mn²⁺-induced quench of fura-2 fluorescence. Together, in AML12 cells, theophylline caused Ca²⁺-associated cytotoxicity and induced Ca²⁺ entry through PLC-independent Ca²⁺ release from the endoplasmic reticulum and PKC-insensitive store-operated Ca²⁺ channels. BAPTA-AM with its protective effects may be a potential compound for prevention of theophylline-induced cytotoxicity.

Mechanisms underlying the effect of an oral antihyperglycaemic agent glyburide on calcium ion (Ca2+ ) movement and its related cytotoxicity in prostate cancer cells

Glyburide is an agent commonly used to treat type 2 diabetes and also affects various physiological responses in different models. However, the effect of glyburide on Ca²⁺ movement and its related cytotoxicity in prostate cancer cells is unclear. This study examined whether glyburide altered Ca²⁺ signalling and viability in PC3 human prostate cancer cells and investigated those underlying mechanisms. Intracellular Ca²⁺ concentrations ([Ca²⁺ ]_i ) in suspended cells were measured by using the fluorescent Ca²⁺ -sensitive dye fura-2. Cell viability was examined by WST-1 assay. Glyburide at concentrations of 100-1000 μM induced [Ca²⁺ ]_i rises. Ca²⁺ removal reduced the signal by approximately 60%. In Ca²⁺ -containing medium, glyburide-induced Ca²⁺ entry was inhibited by 60% by protein kinase C (PKC) activator (phorbol 12-myristate 13 acetate, PMA) and inhibitor (GF109203X), and modulators of store-operated Ca²⁺ channels (nifedipine, econazole and SKF96365). Furthermore, glyburide induced Mn²⁺ influx suggesting of Ca²⁺ entry. In Ca²⁺ -free medium, inhibition of phospholipase C (PLC) with U73122 significantly inhibited glyburide-induced [Ca²⁺ ]_i rises. Treatment with the endoplasmic reticulum (ER) Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) abolished glyburide-evoked [Ca²⁺ ]_i rises. Conversely, treatment with glyburide abolished BHQ-evoked [Ca²⁺ ]_i rises. Glyburide at 100-500 μM decreased cell viability, which was not reversed by pretreatment with the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Together, in PC3 cells, glyburide induced [Ca²⁺ ]_i rises by Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ channels and Ca²⁺ release from the ER in a PLC-dependent manner. Glyburide also caused Ca²⁺ -independent cell death. This study suggests that glyburide could serve as a potential agent for treatment of prostate cancer.

Ca2+ signalling in mouse urethral smooth muscle in situ: role of Ca2+ stores and Ca2+ influx mechanisms

KEY POINTS

Contraction of urethral smooth muscle cells (USMCs) contributes to urinary continence. Ca2+ signalling in USMCs was investigated in intact urethral muscles using a genetically encoded Ca2+ sensor, GCaMP3, expressed selectively in USMCs. USMCs were spontaneously active in situ, firing intracellular Ca2+ waves that were asynchronous at different sites within cells and between adjacent cells. Spontaneous Ca2+ waves in USMCs were myogenic but enhanced by adrenergic or purinergic agonists and decreased by nitric oxide. Ca2+ waves arose from inositol trisphosphate type 1 receptors and ryanodine receptors, and Ca2+ influx by store-operated calcium entry was required to maintain Ca2+ release events. Ca2+ release and development of Ca2+ waves appear to be the primary source of Ca2+ for excitation-contraction coupling in the mouse urethra, and no evidence was found that voltage-dependent Ca2+ entry via L-type or T-type channels was required for responses to α adrenergic responses.

ABSTRACT

Urethral smooth muscle cells (USMCs) generate myogenic tone and contribute to urinary continence. Currently, little is known about Ca2+ signalling in USMCs in situ, and therefore little is known about the source(s) of Ca2+ required for excitation-contraction coupling. We characterized Ca2+ signalling in USMCs within intact urethral muscles using a genetically encoded Ca2+ sensor, GCaMP3, expressed selectively in USMCs. USMCs fired spontaneous intracellular Ca2+ waves that did not propagate cell-to-cell across muscle bundles. Ca2+ waves increased dramatically in response to the α1 adrenoceptor agonist phenylephrine (10 μm) and to ATP (10 μm). Ca2+ waves were inhibited by the nitric oxide donor DEA NONOate (10 μm). Ca2+ influx and release from sarcoplasmic reticulum stores contributed to Ca2+ waves, as Ca2+ free bathing solution and blocking the sarcoplasmic Ca2+ -ATPase abolished activity. Intracellular Ca2+ release involved cooperation between ryanadine receptors and inositol trisphosphate receptors, as tetracaine and ryanodine (100 μm) and xestospongin C (1 μm) reduced Ca2+ waves. Ca2+ waves were insensitive to L-type Ca2+ channel modulators nifedipine (1 μm), nicardipine (1 μm), isradipine (1 μm) and FPL 64176 (1 μm), and were unaffected by the T-type Ca2+ channel antagonists NNC-550396 (1 μm) and TTA-A2 (1 μm). Ca2+ waves were reduced by the store operated Ca2+ entry blocker SKF 96365 (10 μm) and by an Orai antagonist, GSK-7975A (1 μm). The latter also reduced urethral contractions induced by phenylephrine, suggesting that Orai can function effectively as a receptor-operated channel. In conclusion, Ca2+ waves in mouse USMCs are a source of Ca2+ for excitation-contraction coupling in urethral muscles.

The effect of magnolol on Ca2+ homeostasis and its related physiology in human oral cancer cells

OBJECTIVE

Magnolol, a polyphenol compound from herbal medicines, was shown to alter physiology in various cell models. However, the effect of magnolol on Ca²⁺ homeostasis and its related physiology in oral cancer cells is unclear. This study examined whether magnolol altered Ca²⁺ signaling and cell viability in OC2 human oral cancer cells.

METHODS

Cytosolic Ca²⁺ concentrations ([Ca²⁺]_i) in suspended cells were measured by using the fluorescent Ca²⁺-sensitive dye fura-2. Cell viability was examined by 4-[3-[4-lodophenyl]-2-4(4-nitrophenyl)-2H-5-tetrazolio-1,3-benzene disulfonate] water soluble tetrazolium-1 (WST-1) assay.

RESULTS

Magnolol at concentrations of 20-100 μM induced [Ca²⁺]_i rises. Ca²⁺ removal reduced the signal by approximately 50%. Magnolol (100 μM) induced Mn²⁺ influx suggesting of Ca²⁺ entry. Magnolol-induced Ca²⁺ entry was partially suppressed by protein kinase C (PKC) regulators, and inhibitors of store-operated Ca²⁺ channels. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) abolished magnolol-evoked [Ca²⁺]_i rises. Conversely, treatment with magnolol abolished BHQ-evoked [Ca²⁺]_i rises. Inhibition of phospholipase C (PLC) with U73122 partially inhibited magnolol-induced [Ca²⁺]_i rises. Magnolol at 20-100 μM decreased cell viability, which was not reversed by pretreatment with the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM).

CONCLUSIONS

Together, in OC2 cells, magnolol induced [Ca²⁺]_i rises by evoking partially PLC-dependent Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ entry. Magnolol also caused Ca²⁺-independent cell death. Therefore, magnolol-induced cytotoxicity may not be involved in activation mechanisms associated with intracellular Ca²⁺ mobilization in oral cancer cells.

Effect of tetramethylpyrazine (TMP) on Ca2+ signal transduction and cell viability in a model of renal tubular cells

Tetramethylpyrazine (TMP) is a compound purified from herb. Its effect on Ca²⁺ concentrations ([Ca²⁺ ]_i ) in renal cells is unclear. This study examined whether TMP altered Ca²⁺ signaling in Madin-Darby canine kidney (MDCK) cells. TMP at 100-800 μM induced [Ca²⁺ ]_i rises, which were reduced by Ca²⁺ removal. TMP induced Mn²⁺ influx implicating Ca²⁺ entry. TMP-induced Ca²⁺ entry was inhibited by 30% by modulators of protein kinase C (PKC) and store-operated Ca²⁺ channels. Treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) inhibited 93% of TMP-evoked [Ca²⁺ ]_i rises. Treatment with TMP abolished BHQ-evoked [Ca²⁺ ]_i rises. Inhibition of phospholipase C (PLC) abolished TMP-induced responses. TMP at 200-1000 μM decreased viability, which was not reversed by pretreatment with the Ca²⁺  chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester. Together, in MDCK cells, TMP induced [Ca²⁺ ]_i rises by evoking PLC-dependent Ca²⁺ release from endoplasmic reticulum and Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ entry. TMP also caused Ca²⁺ -independent cell death.

Effects of puerarin on intracellular Ca2+ and cell viability of MDCK renal tubular cells

Puerarin is a natural compound and has been used as herb medication in a number of countries, especially in Asia. The effect of puerarin on Ca²⁺ signaling is unknown in renal cells. This study examined whether puerarin affected Ca²⁺ physiology in MDCK renal tubular cells. Cytosolic free Ca²⁺ levels ([Ca²⁺]_i) were measured using the fluorescent dye fura-2. Cell viability was examined by using WST-1 assay. Puerarin induced [Ca²⁺]_i rises and the response was reduced by removing extracellular Ca²⁺. Puerarin-induced Ca²⁺ entry was not altered by protein kinase C (PKC) activity, but was inhibited by nifedipine. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) or thapsigargin partly inhibited puerarin-evoked [Ca²⁺]_i rises. Inhibition of phospholipase C (PLC) with U73122 did not change puerarin-induced [Ca²⁺]_i rises. Puerarin at 25-50μM caused cytotoxicity, which was not reversed by pretreatment with the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Collectively, in MDCK cells, puerarin induced [Ca²⁺]_i rises by evoking PLC-independent Ca²⁺ release from the endoplasmic reticulum and other unknown stores, and Ca²⁺ entry via nifedipine-sensitive, PKC-insensitive Ca²⁺ entry pathways. Puerarin also caused Ca²⁺-independent cell death.

Amitriptyline modulated Ca2+ signaling and induced Ca2+-independent cell viability in human osteosarcoma cells

Amitriptyline is a widely used tricyclic antidepressant, which acts primarily as a serotonin–norepinephrine reuptake inhibitor. This study examined the effect of amitriptyline on Ca2+ homeostasis and its related mechanism in MG63 human osteosarcoma cells. Amitriptyline evoked cytosolic-free Ca2+ concentrations ([Ca2+]i) rises concentration dependently. Amitriptyline-evoked Ca2+ entry was confirmed by Mn2+-induced quench of fura-2 fluorescence. This entry was inhibited by Ca2+ entry modulators nifedipine, econazole, SKF96365, the protein kinase C (PKC) activator phorbol 12-myristate 13 acetate but was not affected by the PKC inhibitor GF109203X. In Ca2+-free medium, treatment with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin (TG) inhibited amitriptyline-evoked [Ca2+]i rises by 95%. Conversely, treatment with amitriptyline abolished TG-evoked [Ca2+]i rises. Inhibition of phospholipase C (PLC) with U73122 inhibited amitriptyline-evoked [Ca2+]i rises by 70%. Amitriptyline killed cells at 200–500 μM in a concentration-dependent fashion. Chelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid/AM did not reverse amitriptyline-induced cytotoxicity. Collectively, our data suggest that in MG63 cells, amitriptyline induced [Ca2+]i rises by evoking PLC-dependent Ca2+ release from the endoplasmic reticulum and Ca2+ entry via PKC-regulated store-operated Ca2+ entry. Amitriptyline also induced Ca2+-disassociated cell death.

Quercetin relaxes guinea pig gallbladder strips

Quercetin, a phytoestrogen and flavonoid, relaxes intestinal and vascular smooth muscle. The purpose of this study was to determine if quercetin had an effect on gallbladder smooth muscle. An in vitro technique was used to determine the effects of quercetin on gallbladder strips and which system(s) mediated the relaxation. Paired t tests were used; differences between means of P < .05 were considered significant. Adding quercetin before cholecystokinin or KCl produced a significant (P < .001) decrease in the amount of tension (0.80 ± 0.04 vs 0.48 ± 0.04 g cholecystokinin octapeptide and 0.8 ± 0.06 vs 0.54 ± 0.05 g KCl, respectively). When the protein kinase C (PKC) inhibitors bisindolymaleimide IV and chelerythrine Cl^- were simultaneously, a significant (P < .001) reduction in the quercetin-induced relaxation (45.7% ± 4.3% vs 27.6% ± 3.4%) was observed. To determine if protein kinase A (PKA) mediated the quercetin-induced relaxation, PKA inhibitor 14-22 amide myristolated was used. It significantly (P < .05) decreased the amount (40.4% ± 3.7% vs 34.5% ± 3.3%) of quercetin-induced relaxation. The use of 2-APB also significantly (P < .001) reduced the amount of quercetin-induced relaxation (51.2% ± 3.5% vs 14.8% ± 3.6%). l-N^G-methyl-l-arginine acetate salt, a nitric oxide synthase inhibitor, significantly (P < 001) decreased the quercetin-induced relaxation (45.7% ± 4.2% vs 35.2% ± 3.6%). KT5823, a PKC inhibitor, had no effect on the quercetin-induced relaxation. Quercetin blocked extracellular Ca²⁺ entry which affected downstream events such as activation of PKC, PKA, intracellular Ca²⁺ release, and activation of nitric oxide synthase. Quercetin relaxed cholecystokinin octapeptide and KCl-induced tension in a concentration dependent manner. Thus quercetin-induced relaxation was mediated by multiple signaling pathways.

The investigation of minoxidil-induced [Ca2+]i rises and non-Ca2+-triggered cell death in PC3 human prostate cancer cells

Minoxidil is clinically used to prevent hair loss. However, its effect on Ca²⁺ homeostasis in prostate cancer cells is unclear. This study explored the effect of minoxidil on cytosolic-free Ca²⁺ levels ([Ca²⁺]_i) and cell viability in PC3 human prostate cancer cells. Minoxidil at concentrations between 200 and 800 μM evoked [Ca²⁺]_i rises in a concentration-dependent manner. This Ca²⁺ signal was inhibited by 60% by removal of extracellular Ca²⁺. Minoxidil-induced Ca²⁺ influx was confirmed by Mn²⁺-induced quench of fura-2 fluorescence. Pre-treatment with the protein kinase C (PKC) inhibitor GF109203X, PKC activator phorbol 12-myristate 13 acetate (PMA), nifedipine and SKF96365 inhibited minoxidil-induced Ca²⁺ signal in Ca²⁺ containing medium by 60%. Treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-ditert-butylhydroquinone (BHQ) in Ca²⁺-free medium abolished minoxidil-induced [Ca²⁺]_i rises. Conversely, treatment with minoxidil abolished BHQ-induced [Ca²⁺]_i rises. Inhibition of phospholipase C (PLC) with U73122 abolished minoxidil-evoked [Ca²⁺]_i rises. Overnight treatment with minoxidil killed cells at concentrations of 200-600 μM in a concentration-dependent fashion. Chelation of cytosolic Ca²⁺ with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/AM (BAPTA/AM) did not prevent minoxidil's cytotoxicity. Together, in PC3 cells, minoxidil induced [Ca²⁺]_i rises that involved Ca²⁺ entry through PKC-regulated store-operated Ca²⁺ channels and PLC-dependent Ca²⁺ release from the endoplasmic reticulum. Minoxidil-induced cytotoxicity in a Ca²⁺-independent manner.

Effect of 2,5-dimethylphenol on Ca(2+) movement and viability in PC3 human prostate cancer cells

The phenolic compound 2,5-dimethylphenol is a natural product. 2,5-Dimethylphenol has been shown to affect rat hepatic and pulmonary microsomal metabolism. However, the effect of 2,5-dimethylphenol on Ca(2+ )signaling and cyotoxicity has never been explored in any culture cells. This study explored the effect of 2,5-dimethylphenol on cytosolic free Ca(2+ )levels ([Ca(2+)]i) and cell viability in PC3 human prostate cancer cells. 2,5-Dimethylphenol at concentrations between 500 μM and 1000 μM evoked [Ca(2+)]i rises in a concentration-dependent manner. This Ca(2+ )signal was inhibited by approximately half by the removal of extracellular Ca(2+). 2,5-Dimethylphenol-induced Ca(2+ )influx was confirmed by Mn(2+)-induced quench of fura-2 fluorescence. Pretreatment with the protein kinase C (PKC) inhibitor GF109203X, nifedipine or the store-operated Ca(2+ )entry inhibitors (econazole or SKF96365) inhibited 2,5-dimethylphenol-induced Ca(2+ )signal in Ca(2+)-containing medium by ∼30%. Treatment with the endoplasmic reticulum Ca(2+ )pump inhibitor thapsigargin in Ca(2+)-free medium abolished 2,5-dimethylphenol-induced [Ca(2+)]i rises. Conversely, treatment with 2,5-dimethylphenol abolished thapsigargin-induced [Ca(2+)]i rises. Inhibition of phospholipase C (PLC) with U73122 reduced 2,5-dimethylphenol-evoked [Ca(2+)]i rises by ∼80%. 2,5-Dimethylphenol killed cells at concentrations of 350-1000 μM in a concentration-dependent fashion. Chelation of cytosolic Ca(2+ )with 1,2-bis(2-aminophenoxy)ethane-N, N, N', N'-tetraacetic acid/AM (BAPTA/AM) did not prevent 2,5-dimethylphenol's cytotoxicity. Together, in PC3 cells, 2,5-dimethylphenol induced [Ca(2+)]i rises that involved Ca(2+ )entry through PKC-regulated store-operated Ca(2+ )channels and PLC-dependent Ca(2+ )release from the endoplasmic reticulum. 2,5-Dimethylphenol induced cytotoxicity in a Ca(2+)-independent manner.

Ca2+ Signaling and Cell Death Induced by Protriptyline in HepG2 Human Hepatoma Cells

The effect of protriptyline on Ca²⁺ physiology in human hepatoma is unclear. This study explored the effect of protriptyline on [Ca²⁺ ]_i and cytotoxicity in HepG2 human hepatoma cells. Protriptyline (50-150 μM) evoked [Ca²⁺ ]_i rises. The Ca²⁺ entry was inhibited by removal of Ca²⁺ . Protriptyline-induced Ca²⁺ entry was confirmed by Mn²⁺ -induced quench of fura-2 fluorescence. Except nifedipine, econazole, SKF96365, GF109203X, and phorbol 12-myristate 13 acetate did not inhibit Ca²⁺ entry. Treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) inhibited 40% of protriptyline-induced response. Treatment with protriptyline abolished BHQ-induced response. Inhibition of phospholipase C (PLC) suppressed protriptyline-evoked response by 70%. At 20-40 μM, protriptyline killed cells which was not reversed by the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Together, in HepG2 cells, protriptyline induced [Ca²⁺ ]_i rises that involved Ca²⁺ entry through nifedipine-sensitive Ca²⁺ channels and PLC-dependent Ca²⁺ release from endoplasmic reticulum. Protriptyline induced Ca²⁺ -independent cell death.

Curcumin Relaxes Precontracted Guinea Pig Gallbladder Strips via Multiple Signaling Pathways

Background

Curcumin (diferuloymethane) is the active ingredient of the dietary spice turmeric. Curcumin modulates various signalling molecules, including inflammatory agents, transcription factors, protein kinases and cell cycle regulatory proteins. The purpose of this study was to determine if curcumin had an effect on gallbladder motility.

Methods

A pharmacologic in vitro technique was used. Since curcumin relaxed both cholecystokinin octapeptide- (CCK) and KCl-induced tension of guinea pig gallbladder strips in a concentration dependent manner, an in vitro technique was used to determine which second messenger system(s) mediated the observed relaxation. Paired t-tests, t-tests and analysis of variance were used for statistical analysis. Differences between mean values of P < 0.05 were considered significant.

Results

To determine if protein kinase A (PKA) mediated the curcumin-induced relaxation, PKA inhibitor 14-22 amide myristolated (PKA-IM) was used. PKA-IM had no significant effect on the amount of curcumin-induced relaxation. When the protein kinase C (PKC) inhibitors bisindolymaleimide IV and chelerythrine Cl^- were used together, a significant (P < 0.01) reduction in the curcumin-induced relaxation was observed. The use of tetraethylammonium chloride (TEA) caused a significant (P < 0.01) decrease in the amount of curcumin-induced relaxation. Adding curcumin prior to the KCl caused a significant (P < 0.001) decrease in the amount of KCl-induced tension.

Conclusions

The results suggested that the curcumin-induced relaxation is mediated by multiple signaling pathways including the PKC second messenger system, inhibiting extracellular Ca²⁺ entry and K+ channels.

Naproxen-induced Ca2+ movement and death in MDCK canine renal tubular cells

Naproxen is an anti-inflammatory drug that affects cellular calcium ion (Ca(2+)) homeostasis and viability in different cells. This study explored the effect of naproxen on [Ca(2+)](i) and viability in Madin-Darby canine kidney cells (MDCK) canine renal tubular cells. At concentrations between 50 μM and 300 μM, naproxen induced [Ca(2+)](i) rises in a concentration-dependent manner. This Ca(2+) signal was reduced partly when extracellular Ca(2+) was removed. The Ca(2+) signal was inhibited by a Ca(2+) channel blocker nifedipine but not by store-operated Ca(2+) channel inhibitors (econazole and SKF96365), a protein kinase C (PKC) activator phorbol 12-myristate 13-acetate, and a PKC inhibitor GF109203X. In Ca(2+)-free medium, pretreatment with 2,5-di-tert-butylhydroquinone or thapsigargin, an inhibitor of endoplasmic reticulum Ca(2+) pumps, partly inhibited naproxen-induced Ca(2+) signal. Inhibition of phospholipase C with U73122 did not alter naproxen-evoked [Ca(2+)](i) rises. At concentrations between 15 μM and 30 μM, naproxen killed cells in a concentration-dependent manner, which was not reversed by prechelating cytosolic Ca(2+) with the acetoxymethyl ester of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl. Annexin V/propidium iodide staining data suggest that naproxen induced apoptosis. Together, in MDCK renal tubular cells, naproxen induced [Ca(2+)](i) rises by inducing Ca(2+) release from multiple stores that included the endoplasmic reticulum and Ca(2+) entry via nifedipine-sensitive Ca(2+) channels. Naproxen induced cell death that involved apoptosis.

The Resveratrol-induced Relaxation of Cholecystokinin Octapeptide- or KCl-induced Tension in Male Guinea Pig Gallbladder Strips Is Mediated Through L-type Ca2+Channels

Background/Aims

Resveratrol (3,5,4′-trihydroxystilbene) is a polyphenolic compound (stilbene) and a phytoalexin. The purpose of this study was to determine the mechanism which mediated the resveratrol-induced relaxation of cholecystokinin octapeptide- or KCl-induced tension in male guinea pig gallbladder strips.

Methods

Gallbladder strips were prepared and suspended in in vitro chambers filled with Krebs-Henseleit solution. The strips were attached to force displacement transducers, and the changes in tension were recorded on a polygraph. All reagents were added directly into the chambers.

Results

To determine if intracellular Ca²⁺ release mediated the resveratrol-induced relaxation of cholecystokinin octapeptide-induced tension, 2-aminoethoxydiphenylborane (2-APB) was used. 2-APB significantly (P < 0.01) decreased the amount of RSVL-induced relaxation. To determine if protein kinase A (PKA) mediated the resveratrol-induced relaxation, PKA inhibitor 14-22 amide myristolated (PKA-IM) was used. PKA-IM had no effect on resveratrol-induced relaxation. Neither KT5823, N^G-methyl-L-arginine acetate salt, a nitric oxide synthase inhibitor, nor fulvestrant had a significant effect on the amount of resveratrol-induced relaxation. Genistein, a protein tyrosine kinase inhibitor, significantly (P < 0.01) increased the RSVL-induced relaxation. To determine if protein kinase C mediated the RSVL-induced relaxation, the protein kinase C inhibitors bisindolymaleimide IV and chelerythrine Cl- were used together, and a significant (P < 0.05) increase in resveratrol-induced relaxation was observed. The pretreatment of the strips with resveratrol significantly (P < 0.001) decreased the amount of KCl- and cholecystokinin octapep-tide-induced tension.

Conclusions

Resveratrol-induced relaxation is mediated by its effects on L-type Ca²⁺ channels and intracellular Ca²⁺ release.

Ca(2+) movement and apoptosis induced by deltamethrin in Madin-Darby canine kidney canine renal tubular cells

This study explored the effect of deltamethrin, a pesticide, on free Ca(2+) concentration [Ca(2+)]i, viability, and apoptosis in Madin-Darby canine kidney (MDCK) canine renal tubular cells. Deltamethrin at concentrations between 10μM and 40μM evoked [Ca(2+)]i rises in a concentration-dependent manner. The Ca(2+) entry was inhibited by nifedipine, econazole, phorbol 12-myristate 13-acetate, and SKF96365. Treatment with the endoplasmic reticulum Ca(2+) pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) in a Ca(2+)-free medium abolished deltamethrin-induced [Ca(2+)]i rise. Treatment with deltamethrin also abolished BHQ-induced [Ca(2+)]i rise. Inhibition of phospholipase C (PLC) activity with U73122 abolished deltamethrin-evoked [Ca(2+)]i rise. Deltamethrin killed cells at 30-60μM in a concentration-dependent manner. The cytotoxic effect of deltamethrin was not reversed by prechelating cytosolic Ca(2+) with the acetoxymethyl ester of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. Annexin V/propidium iodide staining data suggest that 30-50μM deltamethrin induced apoptosis. Together, in MDCK renal tubular cells, deltamethrin induced [Ca(2+)]i rises that involved Ca(2+) entry through protein kinase C-mediated store-operated Ca(2+) channels, and PLC-dependent Ca(2+) release from the endoplasmic reticulum. Deltamethrin also induced Ca(2+)-independent cell death that might involve apoptosis.

Effect of deoxycholic acid on Ca2+ movement, cell viability and apoptosis in human gastric cancer cells

Deoxycholic acid (DOA) is one of the secondary bile acids used as a mild detergent for the isolation of membrane associated proteins. This study examined whether the secondary bile acid, DOA, altered Ca(2+) movement, cell viability and apoptosis in SCM1 human gastric cancer cells. The Ca(2+)-sensitive fluorescent dye fura-2 was used to measure [Ca(2+)]i. DOA-evoked [Ca(2+)]i rises concentration dependently. The response was reduced by removing extracellular Ca(2+). DOA-evoked Ca(2+) entry was inhibited by store-operated Ca(2+) channel inhibitors (nifedipine, econazole and SKF96365), the protein kinase C (PKC) activator phorbol 12-myristate 13 acetate (PMA) and the PKC inhibitor GF109203X. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin (TG) abolished DOA-evoked [Ca(2+)]i rises. Conversely, treatment with DOA abolished TG-evoked [Ca(2+)]i rises. Inhibition of phospholipase C with U73122 abolished DOA-evoked [Ca(2+)]i rises. At 100-500 μM, DOA decreased cell viability, which was not changed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). DOA between 100 and 300 μM also induced apoptosis. Collectively, in SCM1 cells, DOA-induced [Ca(2+)]i rises by evoking phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via store-operated Ca(2+) channels. DOA also caused Ca(2+)-independent apoptosis.

Effect of melamine on [Ca(2+)]i and viability in PC3 human prostate cancer cells

Melamine is thought to be an endocrine disrupter that affects physiology in cells. This study examined the effect of melamine on cytosolic free Ca(2+) concentrations ([Ca(2+)]i) and viability in PC3 human prostate cancer cells. Melamine evoked [Ca(2+)]i rises concentration-dependently. Melamine-evoked Ca(2+) entry was inhibited by nifedipine, econazole, SKF96365, GF109203X and phorbol 12-myristate 13 acetate. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin inhibited melamine-evoked [Ca(2+)]i rise. Conversely, treatment with melamine abolished thapsigargin-evoked [Ca(2+)]i rise. Inhibition of phospholipase C with U73122 did not alter melamine-evoked [Ca(2+)]i rise. Melamine at 500-800μM decreased cell viability, which was not reversed by pretreatment with the Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Collectively, our data suggest that in PC3 cells, melamine induced [Ca(2+)]i rises by evoking phospholipase C-independent Ca(2+) release from the endoplasmic reticulum, and Ca(2+) entry via protein kinase C-regulated store-operated Ca(2+) entry. Melamine also caused Ca(2+)-independent cell death.

Celecoxib-induced increase in cytosolic Ca(2+) levels and apoptosis in HA59T human hepatoma cells

Celecoxib has been shown to have antitumor effect in previous studies but the mechanisms are unclear. The effect of celecoxib on cytosolic Ca(2+) concentrations ([Ca(2+)]i) and viability in HA59T human hepatoma cells was explored. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)]i. Celecoxib at concentrations of 10-50 μM induced a [Ca(2+)]i rise in a concentration-dependent manner. The response was reduced by 80% by removing Ca(2+). Celecoxib induced Mn(2+) influx, leading to quenching of fura-2 fluorescence. Celecoxib-evoked Ca(2+) entry was suppressed by nifedipine, econazole, SK&F96365, and protein kinase C modulators. In the absence of extracellular Ca(2+), incubation with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin nearly abolished celecoxib-induced [Ca(2+)]i rise. Incubation with celecoxib abolished thapsigargin-induced [Ca(2+)]i rise. Inhibition of phospholipase C with U73122 abolished celecoxib-induced [Ca(2+)]i rise. At 1-50 μM, celecoxib inhibited cell viability by less than 20%, which was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N, N, N', N'-tetraacetic acid/acetoxy methyl (BAPTA/AM). Celecoxib (10-50 μM) also induced apoptosis. In sum, in HA59T hepatoma cells, celecoxib induced a [Ca(2+)]i rise by evoking phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via protein kinase C-sensitive store-operated Ca(2+) channels. Celecoxib also caused cell death via apoptosis.

The mechanism of bifonazole-induced [Ca(2+)]i rises and non-Ca(2+)-triggered cell death in PC3 human prostate cancer cells

Bifonazole is an antifungal drug widely used for treating skin diseases. The effect of bifonazole on physiology of cancer cells is unclear. The effect of bifonazole on cytosolic free Ca(2+) concentrations ([Ca(2+)]i) and viability in PC3 human prostate cancer cells was explored. The Ca(2+)-sensitive fluorescent dye, fura-2, was applied to measure [Ca(2+)]i. Bifonazole at concentrations of 5-30 µM induced a [Ca(2+)]i rise in a concentration-dependent manner. The response was reduced by 50% by removing extracellular Ca(2+). Bifonazole-evoked [Ca(2+)]i rise was not altered by nifedipine, econazole, SK&F96365 and protein kinase C activator, but was inhibited by 75% by GF109203X, a protein kinase C inhibitor. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) nearly abolished bifonazole-evoked [Ca(2+)]i rise. Conversely, treatment with bifonazole abolished BHQ-evoked [Ca(2+)]i rise. Inhibition of phospholipase C with U73122 abolished bifonazole-induced [Ca(2+)]i rise. At 30-100 µM, bifonazole decreased cell viability concentration-dependently, which was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N″,N'-tetraacetic acid/acetoxy methyl. Annexin V/propidium iodide staining data suggest that bifonazole (30-100 µM) induced apoptosis concentration-dependently. Together, in PC3 human prostate cancer cells, bifonazole induced [Ca(2+)]i rises by inducing phospholipase C- and protein kinase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) influx via non-store-operated pathways. Bifonazole induced cell death that might involve apoptosis.

Effect of the environmental pollutant bisphenol A dimethacylate (BAD) on Ca2+ movement and viability in OC2 human oral cancer cells

The environmental pollutant bisphenol A dimethacylate (BAD) has been used as a dental composite. The effect of BAD on cytosolic Ca(2+) concentrations ([Ca(2+)]i) and viability in OC2 human oral cancer cells was explored. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)]i. BAD induced [Ca(2+)]i rises in a concentration-dependent manner. The response was reduced by removing extracellular Ca(2+). BAD-evoked Ca(2+) entry was suppressed by nifedipine, econazole, and SK&F96365. In Ca(2+)-free medium, incubation with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin abolished BAD-induced [Ca(2+)]i rise. Inhibition of phospholipase C with U73122 did not alter BAD-induced [Ca(2+)]i rise. At 10-30μM, BAD inhibited cell viability, which was not reversed by chelating cytosolic Ca(2+). BAD (20-30μM) also induced apoptosis. Collectively, in OC2 cells, BAD induced a [Ca(2+)]i rise by evoking phospholipase C-independent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via store-operated Ca(2+) channels. BAD also caused apoptosis.

Effect of diindolylmethane on Ca2+ homeostasis and viability in MDCK renal tubular cells

The effect of the natural product diindolylmethane (DIM) on cytosolic Ca2+ concentrations ([Ca2+]i) and viability in MDCK renal tubular cells was explored. The Ca2+-sensitive fluorescent dye fura-2 was applied to measure [Ca2+]i. DIM at concentrations 1–50 μM induced a [Ca2+]i rise in a concentration-dependent manner. The response was reduced partly by removing Ca2+. DIM induced Mn2+ influx leading to quenching of fura-2 fluorescence. DIM-evoked Ca2+ entry was suppressed by nifedipine, econazole, SK&F96365 and protein kinase C modulators. In the absence of extracellular Ca2+, incubation with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin (TG) or 2,5-di-tert-butylhydroquinone (BHQ) greatly inhibited DIM-induced [Ca2+]i rise. Incubation with DIM abolished TG or BHQ-induced [Ca2+]i rise. Inhibition of phospholipase C with U73122 reduced DIM-induced [Ca2+]i rise by 50%. At 1, 10, 40 and 50 μM, DIM slightly enhanced cell proliferation. The effect of 50 μM DIM was reversed by chelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane- N, N, N', N'-tetraacetic acid. In sum, in MDCK cells, DIM induced a [Ca2+]i rise by evoking phospholipase C-dependent Ca2+ release from the endoplasmic reticulum and Ca2+ entry via protein kinase C-sensitive store-operated Ca2+ channels. DIM did not induce cell death.

Effect of sertraline on [Ca2+](i) and viability of human MG63 osteosarcoma cells

The antidepressant, sertraline, has been shown to have diverse in vitro effects. This study examined whether sertraline altered [Ca(2+)](i) in MG63 human osteosarcoma cells by using fura-2 as a Ca(2+)-sensitive fluorescent dye. At 50-200 µM, sertraline induced a [Ca(2+)](i) rise in a concentration-dependent manner. Ca(2+) response was decreased by removing extracellular Ca(2+), suggesting that Ca(2+) entry and release contributed to the [Ca(2+)](i) signal. Sertraline-induced Ca(2+) entry was inhibited by nifedipine, La(3+), Gd(3+), and SK&F96365. When extracellular Ca(2+) was removed, pretreatment with the endoplasmic reticulum (ER) Ca(2+) pump inhibitor, thapsigargin, or 2,5-di-tert-butylhydroquinone (BHQ) abolished the sertraline-evoked [Ca(2+)](i) rise. Incubation with sertraline also abolished the thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C (PLC) with U73122 abolished the sertraline-induced [Ca(2+)](i) rise. At 20-30 µM, overnight treatment with sertraline killed cells in a concentration-dependent manner. The cytotoxic effect of sertraline was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Annexin V/propidium iodide staining data demonstrate that sertraline (30 µM) evoked apoptosis. Sertraline (20 and 30 µM) also increased levels of reactive oxygen species. Together, in human osteosarcoma cells, sertraline evoked a [Ca(2+)](i) rise by inducing PLC-dependent Ca(2+) release from the ER and Ca(2+) entry by L-type Ca(2+) channels and store-operated Ca(2+) channels. Sertraline induced cell death that may involve apoptosis by mitochondrial pathways.

Effect of diindolylmethane on Ca2+ homeostasis and viability in PC3 human prostate cancer cells

The effect of the natural product diindolylmethane on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) and viability in PC3 human prostate cancer cells was explored. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)](i). Diindolylmethane at concentrations of 20-50 µM induced [Ca(2+)](i) rise in a concentration-dependent manner. The response was reduced partly by removing Ca(2+). Diindolylmethane-evoked Ca(2+) entry was suppressed by nifedipine, econazole, SK&F96365, protein kinase C modulators and aristolochic acid. In the absence of extracellular Ca(2+), incubation with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) inhibited or abolished diindolylmethane-induced [Ca(2+)](i) rise. Incubation with diindolylmethane also inhibited thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 reduced diindolylmethane-induced [Ca(2+)](i) rise. At concentrations of 50-100 µM, diindolylmethane killed cells in a concentration-dependent manner. This cytotoxic effect was not altered by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Annexin V/PI staining data implicate that diindolylmethane (50 and 100 µM) induced apoptosis in a concentration-dependent manner. In conclusion, diindolylmethane induced a [Ca(2+)](i) rise in PC3 cells by evoking phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via phospholipase A(2)-sensitive store-operated Ca(2+) channels. Diindolylmethane caused cell death in which apoptosis may participate.

Relaxant mechanisms of 3, 5, 7, 3', 4'-pentamethoxyflavone on isolated human cavernosum

We have investigated effects and mechanisms responsible for the activity of 3, 5, 7, 3', 4'-pentamethoxyflavone (PMF) on isolated human cavernosum. PMF is the major flavone isolated from Kaempferia parviflora claimed to act as an aphrodisiac. PMF caused relaxation of phenylephrine precontracted human cavernosal strips, and this effect was slightly inhibited by N(G)-nitro-l-arginine, a nitric oxide synthase inhibitor, but not by ODQ (soluble guanylate cyclase inhibitor), TEA (tetraethylammonium, blocker of voltage-dependent K(+) channels) or glybenclamide (blocker of ATP-dependent K(+) channels). PMF did not significantly inhibit the relaxant activity of glyceryltrinitrate or acetylcholine on human cavernosal strips precontracted with phenylephrine. In contrast, sildenafil (phosphodiesterase inhibitor) potentiated the relaxant activity of glyceryl trinitrate but not of acetylcholine. In normal Krebs solution with nifedipine (blocker of l-type Ca(2+) channels), or in Ca(2+)-free Krebs solution, PMF caused a further inhibition of human cavernosum contracted with phenylephrine. In human cavernosum treated with thapsigargin (inhibitor of sarcoplasmic reticulum Ca(2+)-ATPase) in Ca(2+)-free medium, PMF suppressed the concentration-response curve of human cavernosum to phenylephrine and a further suppression was found when SKF-96365 (a blocker of store-operated Ca(2+) channels and Y-27632 (inhibitor of Rho-kinase)), but not nifedipine, were added sequentially. Thus, PMF had only a weak effect on the release of nitric oxide, and had no effect as a K(ATP)- or K(Ca) channel opener, a phosphodiesterase inhibitor, a store-operated Ca(2+) channel blocker or a Rho-kinase inhibitor. Therefore, these studies suggest that PMF causes relaxation of human cavernosum through voltage-dependent Ca(2+) channels and other mechanisms associated with calcium mobilization.

Effect of phenethyl isothiocyanate on Ca2+ movement and viability in MDCK canine renal tubular cells

The effect of the natural compound phenethyl isothiocyanate (PEITC) on cytosolic Ca2+ concentrations ([Ca2+]i) and viability in MDCK renal cells is unknown. This study explored whether PEITC changed [Ca2+]i in MDCK cells using the Ca2+-sensitive fluorescent dye fura-2. PEITC at 200–700 μM increased [Ca2+]i in a concentration-dependent manner. The signal was reduced by removing extracellular Ca2+. PEITC-induced Ca2+ influx was inhibited by nifedipine, econazole, SK&F 96365 and protein kinase C modulators. In Ca2+-free medium, treatment with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin (TG) or 2,5-di- tert-butylhydroquinone (BHQ) inhibited PEITC-induced rise in [Ca2+]i. Incubation with PEITC also inhibited TG or BHQ-induced rise in [Ca2+]i. Inhibition of phospholipase C with U73122 abolished PEITC-induced rise in [Ca2+]i. At 15–75 μM, PEITC decreased viability. The cytotoxic effect of PEITC was enhanced by chelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid/acetoxymethyl ester. Annexin V-FITC data suggest that 20 and 50 μM PEITC induced apoptosis. At 10 and 15 μM, PEITC did not increase reactive oxygen species (ROS) production. Together, in renal tubular cells, PEITC-induced rise in [Ca2+]i by inducing phospholipase C-dependent Ca2+ release from endoplasmic reticulum and Ca2+ entry via store-operated Ca2+ channels. PEITC induced apoptosis in a concentration-dependent, ROS/Ca2+-independent manner.

Effect of m-3m3FBS on Ca2+ handling and viability in OC2 human oral cancer cells

The effect of 2,4,6-trimethyl-N-(meta-3-trifluoromethyl-phenyl)-benzenesulfonamide (m-3M3FBS), a presumed phospholipase C activator, on cytosolic free Ca2+ concentrations ([Ca2+]i) in OC2 human oral cancer cells is unclear. This study explored whether m-3M3FBS changed basal [Ca2+]i levels in suspended OC2 cells by using fura-2 as a Ca2+-sensitive fluorescent dye. M-3M3FBS at concentrations between 10-60 μM increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced partly by removing extracellular Ca2+. M-3M3FBS-induced Ca2+ influx was inhibited by the store-operated Ca2+ channel blockers nifedipine, econazole and SK&F96365, and by the phospholipase A2 inhibitor aristolochic acid. In Ca2+-free medium, 30 μM m-3M3FBS pretreatment inhibited the [Ca2+]i rise induced by the endoplasmic reticulum Ca2+ pump inhibitors thapsigargin and 2,5-di-tert-butylhydroquinone (BHQ). Conversely, pretreatment with thapsigargin, BHQ or cyclopiazonic acid partly reduced m-3M3FBS-induced [Ca2+]i rise. Inhibition of inositol 1,4,5-trisphosphate formation with U73122 did not alter m-3M3FBS-induced [Ca2+]i rise. At concentrations between 5 and 100 μM m-3M3FBS killed cells in a concentration-dependent manner. The cytotoxic effect of m-3M3FBS was not reversed by prechelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Propidium iodide staining data suggest that m-3M3FBS (20 or 50 μM) induced apoptosis in a Ca2+-independent manner. Collectively, in OC2 cells, m-3M3FBS induced [Ca2+]i rise by causing inositol 1,4,5-trisphosphate-independent Ca2+ release from the endoplasmic reticulum and Ca2+ influx via phospholipase A2-sensitive store-operated Ca2+ channels. M-3M3FBS also induced Ca2+-independent cell death and apoptosis.

Effect of methoxychlor on Ca(2+) movement and viability in MDCK renal tubular cells

The effect of the insecticide methoxychlor on the physiology of renal tubular cells is unknown. This study aimed to explore the effect of methoxychlor on cytosolic Ca(2+) concentrations ([Ca(2+) ](i) ) in MDCK renal tubular cells using the Ca(2+) -sensitive fluorescent dye fura-2. Methoxychlor at 5-20 μM increased [Ca(2+) ](i) in a concentration-dependent manner. The signal was reduced by 80% by removing extracellular Ca(2+) . Methoxychlor-induced Ca(2+) entry was not affected by nifedipine and SK&F96365 but was inhibited by econazole and protein kinase C modulators. In Ca(2+) -free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) partly inhibited methoxychlor-induced [Ca(2+) ](i) rise. Incubation with methoxychlor also inhibited thapsigargin- or BHQ-induced [Ca(2+) ](i) rise. Inhibition of phospholipase C with U73122 nearly abolished methoxychlor-induced [Ca(2+) ](i) rise. At 5-15 μM, methoxychlor slightly increased cell viability, whereas at 20 μM, it decreased viability. The cytotoxic effect of methoxychlor was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N,N-tetraacetic acid/AM (BAPTA/AM). Annexin V-FITC data suggest that 10 μM methoxychlor inhibited apoptosis, while 20 μM methoxychlor enhanced apoptosis. Methoxychlor (10 and 20 μM) increased the production of reactive oxygen species. Together, in renal tubular cells, methoxychlor induced [Ca(2+) ](i) rise by inducing phospholipase C-dependent Ca(2+) release from multiple stores and Ca(2+) entry via protein kinase C- and econazole-sensitive channels. Methoxychlor slightly enhanced or inhibited cell viability in a concentration-dependent, Ca(2+) -independent manner. Methoxychlor induced cell death that may involve apoptosis via mitochondrial pathways.

3,3'-Diindolylmethane alters Ca2+ homeostasis and viability in MG63 human osteosarcoma cells

The effect of the natural product 3,3'-diindolylmethane (DIM) on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) and viability in MG63 human osteosarcoma cells was explored. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)](i). DIM at concentrations of 40-80 μM induced a [Ca(2+)](i) rise in a concentration-dependent manner. The response was reduced partly by removing Ca(2+). DIM-evoked Ca(2+) entry was suppressed by nifedipine, econazole, SK&F96365 and protein kinase C modulators. In the absence of extracellular Ca(2+), incubation with the endoplasmic reticulum Ca(2+) pump inhibitors thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) inhibited or abolished DIM-induced [Ca(2+)](i) rise. Incubation with DIM also inhibited thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 abolished DIM-induced [Ca(2+)](i) rise. At concentrations of 10-50 μM, DIM killed cells in a concentration-dependent manner. This cytotoxic effect was not altered by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Annexin V/propidium iodide staining data implicate that DIM (20 and 40 μM) induced apoptosis in a concentration-dependent manner. In sum, in MG63 cells, DIM induced a [Ca(2+)](i) rise by evoking phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via protein kinase C-sensitive store-operated Ca(2+) channels. DIM caused cell death that may involve apoptosis.

Effect of thymol on Ca2+ homeostasis and viability in MG63 human osteosarcoma cells

AIMS

The effect of the natural product thymol on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) and viability in MG63 human osteosarcoma cells was examined.

METHODS

The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)](i).

RESULTS

Thymol at concentrations of 200-1,000 μmol/l induced a [Ca(2+)](i) rise in a concentration-dependent fashion. The response was decreased partially by removal of extracellular Ca(2+). Thymol-induced Ca(2+) entry was inhibited by nifedipine, econazole, SK&F96365 and protein kinase C modulators. When extracellular Ca(2+) was removed, incubation with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) inhibited the thymol-induced [Ca(2+)](i) rise. Incubation with thymol also inhibited the thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 abolished the thymol-induced [Ca(2+)](i) rise. At concentrations of 100-600 μmol/l, thymol killed cells in a concentration-dependent manner. This cytotoxic effect was not changed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/AM. Annexin V/propidium iodide staining data suggest that thymol (200 and 400 μmol/l) induced apoptosis in a concentration-dependent manner. Thymol (200 and 400 μmol/l) also increased levels of reactive oxygen species.

CONCLUSIONS

In MG63 cells, thymol induced a [Ca(2+)](i) rise by inducing phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via protein kinase C-sensitive store-operated Ca(2+) channels. Thymol induced cell death that may involve apoptosis via mitochondrial pathways.

Effect of thymol on Ca2+ homeostasis and viability in human glioblastoma cells

The effect of the natural essential oil thymol on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) and viability in human glioblastoma cells was examined. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)](i). Thymol at concentrations of 400-1000 μM induced a [Ca(2+)](i) rise in a concentration-dependent fashion. The response was decreased partially by removal of extracellular Ca(2+). Thymol-induced Ca(2+) signal was not altered by nifedipine, econazole, SK&F96365, and protein kinase C activator phorbol myristate acetate (PMA), but was inhibited by the protein kinase C inhibitor GF109203X. When extracellular Ca(2+) was removed, incubation with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) abolished thymol-induced [Ca(2+)](i) rise. Incubation with thymol also abolished thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 abolished thymol-induced [Ca(2+)](i) rise. At concentrations of 200-800 μM, thymol killed cells in a concentration-dependent manner. This cytotoxic effect was not changed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/acetoxy methyl (BAPTA/AM). Annexin V/propidium iodide staining data suggest that thymol (200, 400 and 600 μM) induced apoptosis in a concentration-dependent manner. Collectively, in human glioblastoma cells, thymol induced a [Ca(2+)](i) rise by inducing phospholipase C- and protein kinase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via non store-operated Ca(2+) channels. Thymol induced cell death that may involve apoptosis.

Investigation of carvedilol-evoked Ca²+ movement and death in human oral cancer cells

The effect of carvedilol on cytosolic free Ca²⁺ concentrations ([Ca²⁺](i)) in OC2 human oral cancer cells is unknown. This study examined if carvedilol altered basal [Ca²⁺](i) levels in suspended OC2 cells by using fura-2 as a Ca²⁺-sensitive fluorescent probe. Carvedilol at concentrations between 10 and 40 µM increased [Ca²⁺](i) in a concentration-dependent fashion. The Ca²⁺ signal was decreased by 50% by removing extracellular Ca²⁺. Carvedilol-induced Ca²⁺ entry was not affected by the store-operated Ca²⁺ channel blockers nifedipine, econazole, and SK&F96365, but was enhanced by activation or inhibition of protein kinase C. In Ca²⁺-free medium, incubation with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin did not change carvedilol-induced [Ca²⁺](i) rise; conversely, incubation with carvedilol did not reduce thapsigargin-induced Ca²⁺ release. Pretreatment with the mitochondrial uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) inhibited carvedilol-induced [Ca²⁺](i) release. Inhibition of phospholipase C with U73122 did not alter carvedilol-induced [Ca²⁺](i) rise. Carvedilol at 5-50 µM induced cell death in a concentration-dependent manner. The death was not reversed when cytosolic Ca²⁺ was chelated with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA/AM). Annexin V/propidium iodide staining assay suggests that apoptosis played a role in the death. Collectively, in OC2 cells, carvedilol induced [Ca²⁺](i) rise by causing phospholipase C-independent Ca²⁺ release from mitochondria and non-endoplasmic reticulum stores, and Ca²⁺ influx via protein kinase C-regulated channels. Carvedilol (up to 50 μM) induced cell death in a Ca²⁺-independent manner that involved apoptosis.

The mechanism of sertraline-induced [Ca(2+) ](i) rise in human PC3 prostate cancer cells

The effect of sertraline, an antidepressant, on cytosolic-free Ca(2+) levels ([Ca(2+) ](i) ) in human cancer cells is unclear. This study examined whether sertraline altered basal [Ca(2+) ](i) levels in suspended PC3 human prostate cancer cells by using fura-2 as a Ca(2+) -sensitive fluorescent probe. At concentrations of 10-150 μM, sertraline induced a [Ca(2+) ](i) rise in a concentration-dependent fashion. The Ca(2+) signal was reduced partly by removing extracellular Ca(2+) indicating that Ca(2+) entry and release both contributed to the [Ca(2+) ](i) rise. Sertraline induced Mn(2+) influx, leading to quench of fura-2 fluorescence suggesting Ca(2+) influx. This Ca(2+) influx was inhibited by the suppression of store-operated Ca(2+) channels or by the modulation of protein kinase C activity. In Ca(2+) -free medium, pre-treatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-(t-butyl)-1,4-hydroquinone nearly abolished sertraline-induced Ca(2+) release. Conversely, pre-treatment with sertraline greatly reduced the inhibitor-induced [Ca(2+) ](i) rise, suggesting that sertraline released Ca(2+) from the endoplasmic reticulum. Inhibition of phospholipase C inhibited sertraline-induced [Ca(2+) ](i) rise. At 20-30 μM, sertraline killed cells in a concentration-dependent manner. The cytotoxic effect of sertraline was enhanced by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/AM. Annexin V-FITC data suggest that sertraline (20 and 30 μM) evoked apoptosis in a concentration-dependent manner. Together, in PC3 human prostate cancer cells, sertraline induced [Ca(2+) ](i) rises by causing phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and via multiple Ca(2+) influx pathways that involve store-operated Ca(2+) channels. Sertraline also induced apoptosis that was not triggered by [Ca(2+) ](i) rise.

Effect of thapsigargin on Ca²+ fluxes and viability in human prostate cancer cells

Effect of the carcinogen thapsigargin on human prostate cancer cells is unclear. This study examined if thapsigargin altered basal [Ca²⁺](i) levels in suspended PC3 human prostate cancer cells by using fura-2 as a Ca²⁺-sensitive fluorescent probe. Thapsigargin at concentrations between 10 nM and 10 µM increased [Ca²⁺](i) in a concentration-dependent fashion. The Ca²⁺ signal was reduced partly by removing extracellular Ca²⁺ indicating that Ca²⁺ entry and release both contributed to the [Ca²⁺](i) rise. This Ca²⁺ influx was inhibited by suppression of phospholipase A2, but not by inhibition of store-operated Ca²⁺ channels or by modulation of protein kinase C activity. In Ca²⁺-free medium, pretreatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-(t-butyl)-1,4-hydroquinone (BHQ) nearly abolished thapsigargin-induced Ca²⁺ release. Conversely, pretreatment with thapsigargin greatly reduced BHQ-induced [Ca²⁺](i) rise, suggesting that thapsigargin released Ca²⁺ from the endoplasmic reticulum. Inhibition of phospholipase C did not change thapsigargin-induced [Ca²⁺](i) rise. At concentrations of 1-10 µM, thapsigargin induced cell death that was partly reversed by chelation of Ca²⁺ with BAPTA/AM. Annexin V/propidium iodide staining data suggest that apoptosis was partly responsible for thapsigargin-induced cell death. Together, in PC3 human prostate cancer cells, thapsigargin induced [Ca²⁺](i) rises by causing phospholipase C-independent Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ influx via phospholipase A2-sensitive Ca²⁺ channels. Thapsigargin also induced cell death via Ca²⁺-dependent pathways and Ca²⁺-independent apoptotic pathways.

Effect of diindolylmethane on Ca(2+) movement and viability in HA59T human hepatoma cells

The effect of diindolylmethane, a natural compound derived from indole-3-carbinol in cruciferous vegetables, on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) and viability in HA59T human hepatoma cells is unclear. This study explored whether diindolylmethane changed [Ca(2+)](i) in HA59T cells. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)](i). Diindolylmethane at concentrations of 1-50 μM evoked a [Ca(2+)](i) rise in a concentration-dependent manner. The signal was reduced by removing Ca(2+). Diindolylmethane-induced Ca(2+) influx was not inhibited by nifedipine, econazole, SK&F96365, and protein kinase C modulators but was inhibited by aristolochic acid. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitors thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) inhibited or abolished diindolylmethane-induced [Ca(2+)](i) rise. Incubation with diindolylmethane inhibited thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 reduced diindolylmethane-induced [Ca(2+)](i) rise. At concentrations of 10-75 μM, diindolylmethane killed cells in a concentration-dependent manner. The cytotoxic effect of diindolylmethane was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. Propidium iodide staining data suggest that diindolylmethane (25-50 μM) induced apoptosis in a concentration-dependent manner. Collectively, in HA59T cells, diindolylmethane induced a [Ca(2+)](i) rise by causing phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) influx via phospholipase A(2)-sensitive channels. Diindolylmethane induced cell death that may involve apoptosis.

The mechanism of sertraline-induced [Ca2+]i rise in human OC2 oral cancer cells

Effect of sertraline, an antidepressant, on cytosolic free Ca(2+) levels ([Ca(2+)](i)) in human cancer cells is unclear. This study examined if sertraline altered basal [Ca(2+)](i) levels in suspended OC2 human oral cancer by using fura-2 as a Ca(2+)-sensitive fluorescent probe. At concentrations of 10-100 μM, sertraline induced a [Ca(2+)](i) rise in a concentration-dependent fashion. The Ca(2+) signal was reduced partly by removing extracellular Ca(2+) indicating that Ca(2+) entry and release both contributed to the [Ca(2+)](i) rise. Sertraline induced Mn(2+) influx, leading to quench of fura-2 fluorescence suggesting Ca(2+) influx. This Ca(2+) influx was inhibited by suppression of phospholipase A2, inhibition of store-operated Ca(2+) channels or by modulation of protein kinase C activity. In Ca(2+)-free medium, pretreatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-(t-butyl)-1,4-hydroquinone (BHQ) nearly abolished sertraline-induced Ca(2+) release. Conversely, pretreatment with sertraline greatly reduced the inhibitor-induced [Ca(2+)](i) rise, suggesting that sertraline released Ca(2+) from the endoplasmic reticulum. Inhibition of phospholipase C did not change sertraline-induced [Ca(2+)](i) rise. Together, in human oral cancer cells, sertraline induced [Ca(2+)](i) rises by causing phospholipase C-independent Ca(2+) release from the endoplasmic reticulum and Ca(2+) influx via store-operated Ca(2+) channels.

Effect of diallyl disulfide on Ca2+ movement and viability in PC3 human prostate cancer cells

The effect of diallyl disulfide (DADS) on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) and viability in PC3 human prostate cancer cells is unclear. This study explored whether DADS changed [Ca(2+)](i) in PC3 cells by using fura-2. DADS at 50-1000 μM increased [Ca(2+)](i) in a concentration-dependent manner. The signal was reduced by removing Ca(2+). DADS-induced Ca(2+) influx was not inhibited by nifedipine, econazole, SK&F96365, and protein kinase C modulators; but was inhibited by aristolochic acid. In Ca(2+)-free medium, pretreatment with the endoplasmic reticulum Ca(2+) pump inhibitors thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) nearly abolished DADS-induced [Ca(2+)](i) rise. Incubation with DADS inhibited thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 did not alter DADS-induced [Ca(2+)](i) rise. At 500-1000 μM, DADS killed cells in a concentration-dependent manner. The cytotoxic effect of DADS was partly reversed by prechelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Propidium iodide staining suggests that DADS (500 μM) induced apoptosis in a Ca(2+)-independent manner. Annexin V/PI staining further shows that 10 μM and 500 μM DADS both evoked apoptosis. DADS also increased reactive oxygen species (ROS) production. Collectively, in PC3 cells, DADS induced [Ca(2+)](i) rise probably by causing phospholipase C-independent Ca(2+) release from the endoplasmic reticulum and Ca(2+) influx via phospholipase A(2)-sensitive channels. DADS induced Ca(2+)-dependent cell death, ROS production, and Ca(2+)-independent apoptosis.

Effect of methoxychlor on Ca2+ handling and viability in OC2 human oral cancer cells

The effect of the insecticide methoxychlor on the physiology of oral cells is unknown. This study aimed to explore the effect of methoxychlor on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) in human oral cancer cells (OC2) by using the Ca(2+)-sensitive fluorescent dye fura-2. Methoxychlor at 5-20 μM increased [Ca(2+)](i) in a concentration-dependent manner. The signal was reduced by 70% by removing extracellular Ca(2+). Methoxychlor-induced Ca(2+) entry was not affected by nifedipine, econazole, SK&F96365 and protein kinase C modulators but was inhibited by the phospholipase A2 inhibitor aristolochic acid. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) inhibited or abolished methoxychlor-induced [Ca(2+)](i) rise. Incubation with methoxychlor also inhibited thapsigargin- or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 did not alter methoxychlor-induced [Ca(2+)](i) rise. At 5-20 μM, methoxychlor killed cells in a concentration-dependent manner. The cytotoxic effect of methoxychlor was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/AM (BAPTA/AM). Annexin V-FITC data suggest that methoxychlor (10 and 20 μM) evoked apoptosis in a concentration-dependent manner. Together, in human OC2, methoxychlor induced a [Ca(2+)](i) rise probably by inducing phospholipase C-independent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via phospholipase A(2)-sensitive channels. Methoxychlor induced cell death that may involve apoptosis.

Effect of the antidepressant sertraline on Ca2+ fluxes in Madin-Darby canine renal tubular cells

The effect of the antidepressant sertraline on cytosolic-free Ca2+ concentrations ([Ca2+]i) in Madin Darby canine kidney (MDCK) cells is unclear. This study explored whether sertraline changed basal [Ca2+]i levels in suspended MDCK cells by using fura-2 as a Ca2+-sensitive fluorescent dye. Sertraline at concentrations between 1 and 100 microM increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced partly by removing extracellular Ca2+ implicating Ca2+ entry and release both contributed to the [Ca2+]i rise. Sertraline induced Mn2+ influx, leading to quench of fura-2 fluorescence, suggesting Ca2+ influx. This Ca2+ influx was inhibited by suppression of phospholipase A2 but not by store-operated Ca2+ channel blockers and protein kinase C/A modulators. In Ca2+-free medium, pretreatment with the endoplasmic reticulum Ca2+ pump inhibitors nearly abolished sertraline-induced Ca2+ release. Conversely, pretreatment with sertraline partly reduced inhibitor-induced [Ca2+]i rise, suggesting that sertraline released Ca2+ from endoplasmic reticulum. Inhibition of phospholipase C did not much alter sertraline-induced [Ca2+]i rise. Collectively, in MDCK cells, sertraline induced [Ca2+]i rises by causing phospholipase C-independent Ca2+ release from the endoplasmic reticulum and Ca2+ influx via phospholipase A2-sensitive Ca2+ channels.

Carvedilol-induced elevation in cytosolic free Ca(2+) level and apoptosis in SIRC corneal epithelial cells

The effect of the cardiovascular drug carvedilol on cytosolic free Ca(2+) concentrations ([Ca( 2+)](i)) and viability was examined in Statens Seruminstitut rabbit cornea (SIRC) corneal epithelial cells. [Ca(2+)](i) and cell viability were measured using the fluorescent dyes fura-2 and 4-[3-[4-lodophenyl]-2-4(4-nitrophenyl)-2H-5-tetrazolio-1,3-benzene disulfonate] (WST-1), respectively. Carvedilol at concentrations between 1 and 30 microM increased [Ca( 2+)](i) in a concentration-dependent manner. The Ca(2+) signal was reduced partly by removing extracellular Ca(2+). Carvedilol induced Mn(2+) quench of fura-2 fluorescence implicating Ca(2+) influx. The Ca(2+) influx was inhibited by suppression of protein kinase C activity. In Ca(2+)-free medium, after pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca( 2+) pump inhibitor), carvedilol-induced [Ca(2+)](i) rise was reduced; and conversely, carvedilol pretreatment inhibited a major part of thapsigargin-induced [Ca( 2+)](i) rise. Addition of the phospholipase C inhibitor 1-[6-[[17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl]amino] hexyl]-1H-pyrrole-2,5-dione (U73122; 2 microM) did not change carvedilol-induced [Ca(2+)](i) rise. At concentrations between 5 and 70 microM, carvedilol killed cells in a concentration-dependent manner. The cytotoxic effect of 20 microM carvedilol was not reversed by prechelating cytosolic Ca(2+) with BAPTA/AM. Apoptosis was induced by 5-70 microM carvedilol. Collectively, in SIRC corneal epithelial cells, carvedilol-induced [Ca(2+)](i) rises by causing Ca(2+) release from the endoplasmic reticulum in a phospholipase C-independent manner, and Ca( 2+) influx via protein kinase C-regulated Ca(2+) channels. Carvedilol-caused cytotoxicity was mediated by Ca(2+)-independent apoptosis in a concentration-dependent manner.

Effect of m-3M3FBS on Ca(2+) movement in Madin-Darby canine renal tubular cells

The effect of 2,4,6-trimethyl-N-(meta-3-trifluoromethyl-phenyl)-benzenesulfonamide (m-3M3FBS), a presumed phospholipase C (PLC) activator, on cytosolic free Ca(2+) concentrations ([Ca( 2+)](i)) in Madin-Darby canine kidney (MDCK) cells is unclear. This study explored whether m-3M3FBS changed basal [Ca(2+)](i) levels in suspended MDCK cells using fura-2 as a Ca(2+)-sensitive fluorescent dye. M-3M3FBS at concentrations between 0.1 and 20 microM increased [Ca(2+)](i) in a concentration-dependent manner. The Ca(2+) signal was decreased by removing extracellular Ca(2+). M-3M3FBS-induced Ca(2+) influx was inhibited by the store-operated Ca(2+) channel blockers nifedipine, econazole, and SK&F96365, and by the phospholipase A2 inhibitor aristolochic acid. In Ca(2+)-free medium, 20-microM m-3M3FBS pretreatment abolished the [Ca(2+)](i) rise induced by the endoplasmic reticulum Ca(2+) pump inhibitors thapsigargin (TG) and cyclopiazonic acid (CPA). Conversely, pretreatment with TG or CPA partly reduced m-3M3FBS-induced [Ca(2+)](i) rise. The inhibition of PLC with U73122 did not alter m-3M3FBS-induced [Ca(2+)](i) rise. Collectively, in MDCK cells, m-3M3FBS induced [Ca(2+)](i) rises by causing PLC-independent Ca(2+) release from the endoplasmic reticulum and Ca(2+) influx via store-operated Ca(2+) channels and other unidentified Ca(2+) channels.