The nature and role of potassium (K) and water transport mediating hyposmotically-induced regulatory volume decrease (RVD) were studied in nematocytes dissociated with 605 mM thiocyanate from acontia of the Anthozoan Aiptasia diaphana
. Cell volume and hence RVD were calculated from the inverse ratios of the cross sectional areas of nematocytes (A/Ao
) measured before (Ao
) and after (A) challenge with 65% artificial sea water (ASW). To distinguish between K channels and K-Cl cotransport (KCC), external sodium (Na) and chloride (Cl) were replaced by K and nitrate (NO3
), respectively. Inhibitors were added to identify K channels (barium, Ba), and putative kinase (N-ethylmaleimide, NEM) and phosphatase (okadaic acid, OA) regulation of KCC. In 65% NaCl ASW, nematocytes displayed a biphasic change in A/Ao
, peaking within 4 min due to osmotic water entry and thereafter declining within 6 min due to RVD. Changing NaCl to KCl or NaNO3
ASW did not affect the osmotic phase but attenuated RVD, consistent with K channel and KCC mechanisms. Ba (3 mM) inhibited RVD. NEM and OA, applied separately, inhibited the osmotic phase and muted RVD suggesting primary action on water transport (aquaporins). NEM and OA together reduced the peak A/Ao
ratio during the osmotic phase whereas RVD was inhibited when OA preceded NEM. Thus, both K channels and KCC partake in the nematocyte RVD, the extent of which is determined by functional thiols and dephosphorylation of putative aquaporins facilitating the preceding osmotic water shifts.
Giuseppina La Spada, Ph.D.
Dept of Life Sciences “M. Malpighi”
Section of General Physiology and Pharmacology
Via F. Stagno D’Alcontres 31, 98166 Messina (Italy)
Tel. +39.090.6765209-06, Fax +39.090.394030, E-Mail email@example.com
Accepted: June 02, 2010
Published online: August 24, 2010
Number of Print Pages : 10
Cellular Physiology and Biochemistry (International Journal of Experimental Cellular Physiology, Biochemistry andPharmacology)
Vol. 26, No. 2, Year 2010 (Cover Date: 2010)
Journal Editor: F. Lang, Tübingen
ISSN: 1015–8987 (Print), eISSN: 1421–9778 (Online)
For additional information: http://www.karger.com/journals/cpb
Copyright / Drug Dosage
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 or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
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 goverment 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.