title: In vivo and in vitro effects of high-K(+) stress on branchial expression of ROMKa in seawater-acclimated Mozambique tilapia.
abstract: Recently, a teleost ortholog of renal outer medullary K(+) channel (ROMK) expressed in gill ionocytes (ROMKa) has emerged as a primary K(+)-excreting pathway in fish. However, the mechanisms by which ROMKa expression is regulated in response to perturbations of plasma K(+) levels are unknown. In this study, we aimed to identify potential links between the endocrine system and K(+) regulation in a euryhaline fish. We assessed time-course changes in multiple endocrine parameters, including plasma cortisol and gene expression of branchial glucocorticoid and mineralocorticoid receptors (GR1, GR2, and MR) and pituitary hormones, in seawater (SW)-acclimated Mozambique tilapia (Oreochromis mossambicus) exposed to high-K(+) (H-K) SW. Exposure to H-K SW elicited little effects on plasma cortisol or mRNA levels of GRs and pituitary hormones. Since plasma K(+) and branchial ROMKa expression was increased within 6h after H-K treatment in vivo, the effect of high K(+) was subsequently tested in a gill filament incubation experiment using media with differing K(+) concentrations. ROMKa mRNA levels were induced following incubation of filaments in H-K medium for 6h. The present study is the first to demonstrate that the expression of ROMKa in teleost ionocytes can respond to high K(+) conditions independent from systemic signaling.
authors.affiliation: Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan. Electronic address: fumiya@marine.fs.a.u-tokyo.ac.jp.
authors.forename: Fumiya
authors.initials: F
authors.lastname: Furukawa
authors.affiliation: Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
authors.forename: Soichi
authors.initials: S
authors.lastname: Watanabe
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA.
authors.forename: Andre P
authors.initials: AP
authors.lastname: Seale
authors.affiliation: Department of Biology, Skidmore College, Saratoga Springs, NY 12866, USA.
authors.forename: Jason P
authors.initials: JP
authors.lastname: Breves
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA.
authors.forename: Darren T
authors.initials: DT
authors.lastname: Lerner
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA.
authors.forename: E Gordon
authors.initials: EG
authors.lastname: Grau
authors.affiliation: Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
authors.forename: Toyoji
authors.initials: T
authors.lastname: Kaneko
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D006854:Hydrocortisone / Q000097:blood; D066298:In Vitro Techniques; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D011965:Receptors, Glucocorticoid / Q000235:genetics; D018161:Receptors, Mineralocorticoid / Q000235:genetics; D012623:Seawater; D017210:Tilapia / Q000502:physiology*
chemical_list: D015221:Potassium Channels; D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D011188:Potassium; D006854:Hydrocortisone
keywords: Cortisol; Ionocyte; Oreochromis mossambicus; Pituitary; Potassium; ROMK