title: Murine vasa recta pericyte chloride conductance is controlled by calcium, depolarization, and kinase activity.
abstract: We used the whole cell patch-clamp technique to investigate the regulation of descending vasa recta (DVR) pericyte Ca(2+)-dependent Cl(-) currents (CaCC) by cytoplasmic Ca(2+) concentration ([Ca](CYT)), voltage, and kinase activity. Murine CaCC increased with voltage and electrode Ca(2+) concentration. The current saturated at [Ca](CYT) of ∼1,000 nM and exhibited an EC(50) for Ca(2+) of ∼500 nM, independent of depolarization potential. Activation time constants were between 100 and 200 ms, independent of electrode Ca(2+). Repolarization-related tail currents elicited by stepping from +100 mV to varying test potentials exhibited deactivation time constants of 50-200 ms that increased with voltage when electrode [Ca](CYT) was 1,000 nM. The calmodulin inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7, 30 μM) blocked CaCC. The myosin light chain kinase blockers 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-7, 1-50 μM) and 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-9, 10 μM) were similarly effective. Resting pericytes were hyperpolarized by ML-7. Pericytes exposed to ANG II (10 nM) depolarized from a baseline of -50 ± 6 to -29 ± 3 mV and were repolarized to -63 ± 7 mV by exposure to 50 μM ML-7. The Ca(2+)/calmodulin-dependent kinase inhibitor KN-93 reduced pericyte CaCC only when it was present in the electrode and extracellular buffer from the time of membrane break-in. We conclude that murine DVR pericytes are modulated by [Ca](CYT), membrane potential, and phosphorylation events, suggesting that Ca(2+)-dependent Cl(-) conductance may be a target for regulation of vasoactivity and medullary blood flow in vivo.
authors.affiliation: Division of Nephrology, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: Hai
authors.initials: H
authors.lastname: Lin
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Pallone
authors.forename: Chunhua
authors.initials: C
authors.lastname: Cao
mesh_terms: D000804:Angiotensin II / Q000378:metabolism; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D001596:Benzylamines / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D017136:Ion Transport; D007606:Juxtaglomerular Apparatus / Q000098:blood supply*; D008564:Membrane Potentials; D051379:Mice; D008810:Mice, Inbred C57BL; D055806:Microvessels / Q000187:drug effects / Q000201:enzymology*; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D009281:Naphthalenes / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D020286:Pericytes / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D013997:Time Factors; D000096926:Benzenesulfonamides
chemical_list: D000804:Angiotensin II; D001381:Azepines; D001596:Benzylamines; D002118:Calcium; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002147:Calmodulin; D002712:Chlorides; D009219:Myosin-Light-Chain Kinase; D009281:Naphthalenes; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D013449:Sulfonamides; C056218:ML 9; C070571:ML 7; C072105:KN 93; D000096926:Benzenesulfonamides; C017967:W 7