Chloride transport in mitochondrion-rich cells of euryhaline tilapia (Oreochromis mossambicus) larvae.
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 (20-80 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 microM ouabain or bumetanide inhibited the Cl- secretion by approximately 75%. In freshwater (FW)-acclimated larvae, a lower level of outward Cl- gradients (0.2-1 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 microM metolazone) reduced the flux by approximately 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.
Horng
Jiun-Lin
JL
Institute of Cellular and Organismic Biology, Academia Sinica, Taipei.
Hwang
Pung-Pung
PP
Shih
Tin-Han
TH
Wen
Zhi-Hong
ZH
Lin
Chan-Shing
CS
Lin
Li-Yih
LY
D000818:Animals; D000838:Anions; D002712:Chlorides / Q000378:metabolism*; D015640:Ion Channel Gating; D017136:Ion Transport; D017736:Ion-Selective Electrodes; D015603:Keratinocytes / Q000378:metabolism; D007814:Larva / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D012867:Skin / Q000378:metabolism; D017210:Tilapia / Q000378:metabolism*
D000838:Anions; D002712:Chlorides