title: Ionic currents and endothelin signaling in smooth muscle cells from rat renal resistance arteries.
abstract: The repertoire of ionic channels expressed in myocytes freshly isolated from microdissected interlobar and arcuate arteries of rat kidney and their integrative behavior in response to endothelin-1 (ET-1) were studied by identification and characterization of major whole cell current components using patch-clamp technique. In renal microvascular smooth muscle cells (RMSMC) dialyzed with K(+)-containing solution, rapidly inactivating (Ito) and sustained outward K+ currents were identified. Voltage-dependent Ito was categorized as "A" current based on its kinetics, sensitivity to 4-aminopyridine (4-AP), and refractoriness to tetraethylammonium (TEA+). Ca(2+)-activated component of K+ current was completely blocked by 10 mM TEA+, whereas 5 mM 4-AP did not affect this current. Maximal Ca2+ current (ICa) recorded in Cs(+)-loaded RMSMC reached 250 pA when cells were bathed in a solution with 2.5 mM Ca2+. Two patterns of ICa differing in kinetics, voltage range of activation and inactivation, and sensitivity to nifedipine were identified as T and L currents. Ca(2+)-dependent current component showing reversal potential near Cl- current (ECl) and sensitivity to blocking action of 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid was identified as Ca(2+)-activated ECl. Activation of RMSMC with ET-1 (1-10 nM) induced elevation of [Ca2+]i and subsequent activation of Ca(2+)-activated ICl, which led to membrane depolarization sufficient to activate voltage-gated Ca2+ channels. ET-1-evoked transient reduction of ICa carried through voltage-gated Ca2+ channels was followed by augmentation of L-type ICa. ET-1-induced mobilization of intracellular Ca2+, accompanied by membrane depolarization, resulted in activation of Ca(2+)-dependent K+ channels, which can play the role of a feedback element terminating ET-1-induced membrane depolarization.
authors.affiliation: Department of Medicine, State University of New York at Stony Brook 11794-8152.
authors.forename: D V
authors.initials: DV
authors.lastname: Gordienko
authors.forename: C
authors.initials: C
authors.lastname: Clausen
authors.forename: M S
authors.initials: MS
authors.lastname: Goligorsky
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000502:physiology*; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D003035:Cobalt / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004553:Electric Conductivity; D016232:Endothelins / Q000494:pharmacology*; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D066298:In Vitro Techniques; D007668:Kidney / Q000098:blood supply*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation; D015398:Signal Transduction; D013050:Spectrometry, Fluorescence; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014655:Vascular Resistance
chemical_list: D016232:Endothelins; D005456:Fluorescent Dyes; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; C049925:fura-2-am; D003035:Cobalt; D002110:Caffeine; D004533:Egtazic Acid; D019789:Tetraethylammonium; D015761:4-Aminopyridine; D009543:Nifedipine; D011188:Potassium; D002118:Calcium; D016257:Fura-2