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KMID : 0811719970010050565
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Korean Journal of Physiology & Pharmacology
1997 Volume.1 No. 5 p.565 ~ p.572
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Endothelin Increases Intracellular Free Calcium in Isolated Rat Nephron
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Seok Ho Cha
Young-Jin Cho/Kweon-Haeng Lee/Hitoshi Endou
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Abstract
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In the freshly isolated rat nephron, the effect of endothelin-1, -2 and -3 (ET-1, -2 and -3) on cytosolic free calcium concentration ([Ca2+]i) was determined using the fluorescent indicator Fura-2/AM. [Ca2+]i increase was investigated in 9 parts of the single nephron including glomerulus (Glm), S1,S2,S3, cortical and medullary thick ascending limb and cortical (CCT) and outer medullary collecting tubule (OMCT). Endothelins increased [Ca2+]i in Glm (ET-1; 127±17, ET-2; 93±5, ET-3; 169±17), CCT (ET-1; 30±6, ET-2; 38±19, ET-3; 158±18) and OMCT (ET-1; 197±11, ET-2; 195±11, ET-3; 215±37) at 10-7 M. In OMCT, ET-1 and ET-2 increased [Ca2+]i in a dose-dependent manner (10?10∼10?6 M). To the contrary, ET-3-induced [Ca2+]i rise was begun from 10?12 M. BQ-123Na, an antagonist of ETA receptor, at 10?4 M inhibited about 30% of [Ca2+]i rise induced by ET-1 and -3. Binding experiments using [125I]ET?3 showed the existence of ETB receptor in OMCT. This binding was replaced by ET-1, ET-2 or ET-3 by the almost same degree but not by angiotensin II or vasopressin.
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KEYWORD
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Endothelin, Intracellular free calcium, Outer medullary collecting tubule,
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