Involvement of IP3-receptor activation in endothelin-1-induced Ca(2+) influx in rat pulmonary small artery

• Published in: European journal of pharmacology Vol. 720; no. 1-3; pp. 255 - 263
• Main Authors: Kato, K, Okamura, K, Hatta, M, Morita, H, Kajioka, S, Naito, S, Yamazaki, J
• Format: Journal Article
• Language: English
• Published: Netherlands 15.11.2013
• Subjects: Animals; Calcium - metabolism; Endothelin-1 - metabolism; In Vitro Techniques; Inositol 1,4,5-Trisphosphate Receptors - metabolism; Male; Pulmonary Artery - metabolism; Rats; Rats, Wistar; Receptor, Endothelin A - metabolism; Fura-2; ROCC; IP3; 2APB; Pulmonary artery; Xestospongin C
• ISSN: 1879-0712
• DOI: 10.1016/j.ejphar.2013.09.076

We examined the endothelin-1 (ET-1)-induced increase in the intracellular free Ca(2+) concentration ([Ca(2+)]i) in fura-2-loaded rat pulmonary small arteries. ET-1 (30 nM) elicited a long-lasting increase in [Ca(2+)]i in physiological salt solution (PSS). In subsequent experiments, arteries were pretreated with BQ-788, an ETB-specific blocker, to allow us to focus on responses mediated via the ETA receptor, the existence of which was confirmed by immunohistochemistry. In Ca(2+)-free PSS, ET-1 evoked a small transient increase in [Ca(2+)]i, indicating Ca(2+) release from the SR (sarcoplasmic reticulum). After a switch to PSS (containing 2mM CaCl2), ET-1 elicited a long-lasting increase in [Ca(2+)]i that was not inhibited by 1 μM nicardipine, an L-type Ca(2+)-channel inhibitor, suggesting involvement of a Ca(2+)-influx pathway independent of that channel. In arteries preincubated with 30 μM cyclopiazonic acid (CPA) or 2 μM thapsigargin (TG), the ET-1-induced Ca(2+)-release was greatly reduced, and the induced Ca(2+)-influx was attenuated. U-73122, a phospholipase C (PLC) inhibitor, had inhibitory effects similar to those of CPA and TG on the ET-1-induced Ca(2+)-release and Ca(2+)-influx, whereas U-73343, an inactive analogue of U-73122, had no such effects. Two putative membrane-permeable IP3-receptor blockers, 2-aminoethoxydiphenyl borate (2APB, 50 μM) and Xestospongin C (20 μM), (a) almost completely inhibited the ET-1-induced Ca(2+)-release and Ca(2+)-influx, and (b) reduced the ET-1-induced contraction. These results indicate that in rat pulmonary small arteries, ET-1 induces receptor-operated Ca(2+) influx via the ETA receptor, and that this influx interacts with InsP3-receptor activation.