title: Involvement of IP3-receptor activation in endothelin-1-induced Ca(2+) influx in rat pulmonary small artery.
abstract: 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.
authors.affiliation: Department of Physiological Science and Molecular Biology, Fukuoka Dental College, Fukuoka, Japan; Fukuoka School of Medical Sciences, Fukuoka, Japan. Electronic address: kkatou@college.fdcnet.ac.jp.
authors.forename: K
authors.initials: K
authors.lastname: Kato
authors.forename: K
authors.initials: K
authors.lastname: Okamura
authors.forename: M
authors.initials: M
authors.lastname: Hatta
authors.forename: H
authors.initials: H
authors.lastname: Morita
authors.forename: S
authors.initials: S
authors.lastname: Kajioka
authors.forename: S
authors.initials: S
authors.lastname: Naito
authors.forename: J
authors.initials: J
authors.lastname: Yamazaki
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D019332:Endothelin-1 / Q000378:metabolism*; D066298:In Vitro Techniques; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism*; D008297:Male; D011651:Pulmonary Artery / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D044022:Receptor, Endothelin A / Q000378:metabolism
chemical_list: D019332:Endothelin-1; D053496:Inositol 1,4,5-Trisphosphate Receptors; D044022:Receptor, Endothelin A; D002118:Calcium
keywords: 2APB; Fura-2; IP3; Pulmonary artery; ROCC; Xestospongin C