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This Article Full Text Full Text (PDF) All Versions of this Article: 297/4/C845    most recent 00218.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Horng, J.-L. Articles by Lin, L.-Y. PubMed PubMed Citation Articles by Horng, J.-L. Articles by Lin, L.-Y.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Chloride transport in mitochondrion-rich cells of euryhaline tilapia (Oreochromis mossambicus) larvae

¹Institute of Cellular and Organismic Biology, Academia Sinica, Taipei; ²Department of Life Science, National Taiwan Normal University, Taipei; and ³Department of Marine Biotechnology and Resources, Division of Marine Biotechnology, Asia-Pacific Ocean Research Center, National Sun Yat-sen University, Kaohsiung, Taiwan

Submitted 18 May 2009 ; accepted in final form 29 July 2009

A noninvasive scanning ion-selective electrode technique (SIET) was applied to measure Cl^– transport at individual mitochondrion-rich cells (MRCs) in the skin of euryhaline tilapia (Oreochromis mossambicus) larvae. In seawater (SW)-acclimated larvae, outward Cl^– gradients (2080 mM higher than the background) were measured at the surface, indicating a secretion of Cl^– from the skin. By serial probing over the surface of MRCs and adjacent keratinocytes (KCs), a significant outward flux of Cl^– was detected at the apical opening (membrane) of MRCs. Treatment with 100 µM ouabain or bumetanide inhibited the Cl^– secretion by 75%. In freshwater (FW)-acclimated larvae, a lower level of outward Cl^– gradients (0.21 mM) was measured at the skin surface. Low-Cl^– water (<0.005 mM) acclimation increased the apical Na⁺-Cl^– cotransporter (NCC) immunoreactivity of MRCs in the larval skin. An inward flux of Cl^– was detected when probing the exterior surface of a group of MRCs (convex-MRCs) that express the NCC. An NCC inhibitor (100 µM metolazone) reduced the flux by 90%. This study provides direct and convincing evidence for Cl^– transport by MRCs of SW- and FW-acclimated euryhaline tilapia and the involvement of an apical NCC in Cl^– uptake of MRCs of FW-acclimated fish.

Na⁺-Cl^– cotransporter; osmoregulation; gills; ionocytes; ionoregulation