Distinct Ca2+ signalling mechanisms induced by ATP and sphingosylphosphorylcholine in porcine aortic smooth muscle cells

• Published in: British journal of pharmacology 2000-04, Vol.129 (7), p.1365-1374
• Main Authors: Chin, Ting‐Yu, Chueh, Sheau‐Huei
• Format: Article
• Language: English
• Subjects: Adenosinic and purinergic receptors; aortic smooth muscle cells; Biological and medical sciences; Cell receptors; Cell structures and functions; cytosolic Ca2+ concentration; desensitization; Fundamental and applied biological sciences. Psychology; Medical sciences; Molecular and cellular biology; Neuropharmacology; Neurotransmitters. Neurotransmission. Receptors; Peptidergic system (neuropeptide, opioid peptide, opiates...). Adenosinergic and purinergic systems; Pharmacology. Drug treatments; Purinoceptor; receptor‐operated Ca2+ channel; sphingosylphosphorylcholine; store‐operated Ca2+ channel; voltage‐operated Ca2+ channel
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0703190

The increase in the cytosolic Ca2+ concentration ([Ca2+]i) following repetitive stimulation with ATP or sphingosylphosphorylcholine (SPC) in single porcine aortic smooth muscle cells was investigated using the Ca2+ indicator, fura‐2. The ATP‐induced [Ca2+]i increase resulted from both Ca2+ release and Ca2+ influx. The former was stimulated by phospholipase C activation, while the latter occurred predominantly via the receptor‐operated Ca2+ channels (ROC), rather than the store‐operated Ca2+ channels (SOC) or the voltage‐operated Ca2+ channel (VOC). Furthermore, the P2X5 receptor was shown to be responsible for the ATP‐induced Ca2+ influx. A reproducible [Ca2+]i increase was induced by repetitive ATP stimulation, but was abolished by removal of extracellular Ca2+ or inhibition of intracellular Ca2+ release using U‐73122 or thapsigargin, and was restored by Ca2+ readdition in the former case. SPC only caused Ca2+ release, and the amplitude of the repetitive SPC‐induced [Ca2+]i increases declined gradually. However, a reproducible [Ca2+]i increase was seen in cells in which protein kinase C being inhibited, which increased the SPC‐induced Ca2+ influx, rather than IP3 generation. In conclusion, although the amplitude of the ATP‐induced Ca2+ release, measured when Ca2+ influx was blocked, or of the Ca2+ influx when Ca2+ release was blocked, progressively decreased following repetitive stimulation, the overall [Ca2+]i increase for each stimulation under physiological conditions remained the same, suggesting that the Ca2+ stores were replenished by an influx of Ca2+ during stimulation. The SPC‐induced [Ca2+]i increase resulted solely from Ca2+ release and decreased gradually following repetitive stimulation, but the decrease could be prevented by stimulating Ca2+ influx, further supporting involvement of the intracellular Ca2+ stores in Ca2+ signalling. British Journal of Pharmacology (2000) 129, 1365–1374; doi:10.1038/sj.bjp.0703190