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.