Voltage-Gated Sodium Channels in Human Aortic Smooth Muscle Cells

Abstract

Whole-cell, voltage clamp methods were used to study inward currents in human aortic smooth muscle cells in culture. Cells were plated on glass coverslips, cultured in supplemented M-199 media with 5% serum and studied as primary cells and at passages 2–5. Inward currents were measured with a pipette solution containing Cs⁺ and TEA⁺ to block K⁺ currents and with 2.5 m M [Ca²⁺]₀ in the perfusate. Inward currents activated at about –50 mV, peaked at about –15 mV and reversed at about +30 mV. Values of peak inward current averaged 14.7 ± 3.3 pA/pF and cell capacitance averaged 124 ± 10 pF (n = 35). These currents activated rapidly with a time-to-peak current of 2.4 ± 0.3 ms at a test potential of –10 mV from a holding potential of –80 mV. The current also inactivated rapidly with a time course that could be described by two components with time constants of 1.8 ± 0.2 and 17.8 ± 3.5 ms at –10 mV. The currents decreased when extracellular Na⁺ was reduced and were completely inhibited by 50 n M tetrodotoxin (TTX), suggesting that they represented voltage-gated Na⁺ currents (I_Na). Activation curves were characterized with a V_0.5 = –16.6 ± 2.4 mV and a slope factor k = –5.2 ± 0.2 mV while inactivation curves were characterized with a V_0.5 = –60.9 ± 1.7 mV and a slope factor k = 8.8 ± 0.4 mV. Lowering external [Ca²⁺] to zero increased the maximum I_Na, shifted its voltage dependence in the hyperpolarizing direction and increased the rate of I_Na inactivation. Increasing external [Ca²⁺] or [Mg²⁺]decreased I_Na and slowed its rate of inactivation. These studies demonstrate the presence of voltage-gated Na⁺ channels with high TTX sensitivity that are modulated by extracellular divalent cations in human aortic smooth muscle cells maintained in cell culture. Window currents were found in the voltage range of –50 to –20 mV, suggesting that these channels could contribute to the resting membrane potential.

Journal

Journal ID (publisher-id): JVR

Journal ID (nlm-ta): J Vasc Res

Journal ID (doi): 10.1159/issn.1018-1172

Title: Journal of Vascular Research

Publisher: S. Karger AG

ISSN (Print): 1018-1172

ISSN (Electronic): 1423-0135

Publication date Subscription-year: 1998

Publication date (Print): October 1998

Publication date (Electronic): 28 October 1998

Volume: 35

Issue: 5

Pages: 310-317

Affiliations

Bockus Research Institute, The Graduate Hospital, Department of Physiology, University of Pennsylvania and Departments of Physiology and Surgery, Medical College of Pennsylvania, Philadelphia, Pa., USA

Article

Publisher ID: 25600 Other ID: J Vasc Res 1998;35:310–317

DOI: 10.1159/000025600

PubMed ID: 9789111

Copyright statement: © 1998 S. Karger AG, Basel

License:

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

Page count

Figures: 7, References: 41, Pages: 8

Product

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Categories

Subject: Research Paper