title: Distinct Ca(2+) signalling mechanisms induced by ATP and sphingosylphosphorylcholine in porcine aortic smooth muscle cells.
abstract: 1. The increase in the cytosolic Ca(2+) concentration ([Ca(2+)](i)) following repetitive stimulation with ATP or sphingosylphosphorylcholine (SPC) in single porcine aortic smooth muscle cells was investigated using the Ca(2+) indicator, fura-2. 2. The ATP-induced [Ca(2+)](i) increase resulted from both Ca(2+) release and Ca(2+) influx. The former was stimulated by phospholipase C activation, while the latter occurred predominantly via the receptor-operated Ca(2+) channels (ROC), rather than the store-operated Ca(2+) channels (SOC) or the voltage-operated Ca(2+) channel (VOC). Furthermore, the P2X(5) receptor was shown to be responsible for the ATP-induced Ca(2+) influx. 3. A reproducible [Ca(2+)](i) increase was induced by repetitive ATP stimulation, but was abolished by removal of extracellular Ca(2+) or inhibition of intracellular Ca(2+) release using U-73122 or thapsigargin, and was restored by Ca(2+) readdition in the former case. 4. SPC only caused Ca(2+) release, and the amplitude of the repetitive SPC-induced [Ca(2+)](i) increases declined gradually. However, a reproducible [Ca(2+)](i) increase was seen in cells in which protein kinase C being inhibited, which increased the SPC-induced Ca(2+) influx, rather than IP(3) generation. 5. In conclusion, although the amplitude of the ATP-induced Ca(2+) release, measured when Ca(2+) influx was blocked, or of the Ca(2+) influx when Ca(2+) release was blocked, progressively decreased following repetitive stimulation, the overall [Ca(2+)](i) increase for each stimulation under physiological conditions remained the same, suggesting that the Ca(2+) stores were replenished by an influx of Ca(2+) during stimulation. The SPC-induced [Ca(2+)](i) increase resulted solely from Ca(2+) release and decreased gradually following repetitive stimulation, but the decrease could be prevented by stimulating Ca(2+) influx, further supporting involvement of the intracellular Ca(2+) stores in Ca(2+) signalling.
authors.affiliation: Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan, Republic of China.
authors.forename: T Y
authors.initials: TY
authors.lastname: Chin
authors.forename: S H
authors.initials: SH
authors.lastname: Chueh
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000166:cytology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D008345:Manganese / Q000378:metabolism / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019311:Staurosporine / Q000494:pharmacology; D013552:Swine; D019284:Thapsigargin / Q000494:pharmacology; D013872:Thionucleosides / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D004963:Estrenes; D007093:Imidazoles; D011760:Pyrrolidinones; D013872:Thionucleosides; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; C005356:sphingosine phosphorylcholine; D010767:Phosphorylcholine; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C016957:adenosine-3',5'-cyclic phosphorothioate; C022571:adenosine 5'-O-(3-thiotriphosphate); C021714:2-methylthioadenosine; D008345:Manganese; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D004533:Egtazic Acid; D015759:Ionomycin; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D019311:Staurosporine; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D000241:Adenosine; D013110:Sphingosine; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D002118:Calcium