Murine vasa recta pericyte chloride conductance is controlled by calcium, depolarization, and kinase activity

Hai Lin, Thomas L. Pallone, Chunhua Cao

Abstract

We used the whole cell patch-clamp technique to investigate the regulation of descending vasa recta (DVR) pericyte Ca2+-dependent Cl currents (CaCC) by cytoplasmic Ca2+ concentration ([Ca]CYT), voltage, and kinase activity. Murine CaCC increased with voltage and electrode Ca2+ concentration. The current saturated at [Ca]CYT of ∼1,000 nM and exhibited an EC50 for Ca2+ of ∼500 nM, independent of depolarization potential. Activation time constants were between 100 and 200 ms, independent of electrode Ca2+. 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 Ca2+/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 Ca2+-dependent Cl conductance may be a target for regulation of vasoactivity and medullary blood flow in vivo.

  • kidney
  • medulla
  • microcirculation
  • electrophysiology
  • vasoconstriction
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