Journal
MOLECULAR AND CELLULAR ENDOCRINOLOGY
Volume 422, Issue C, Pages 93-102Publisher
ELSEVIER IRELAND LTD
DOI: 10.1016/j.mce.2015.12.001
Keywords
NCC; Sodium absorption; Ionocyte; Cortisol; Zebrafish
Categories
Funding
- Academia Sinica [103-7]
- Ministry of Science and Technology of Taiwan (MOST) [103-2321-B-001-010]
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In mammals, sodium/hydrogen exchanger (NHE) and sodium-chloride cotransporter (NCC) are expressed in renal tubules, and exhibit functional redundancy and mutual compensation in Na+ uptake. In teleosts, the gills of the adult and skin of the embryonic stage function as external kidneys, and ionocytes are responsible for ionoregulation in these tissues. NHE- and NCC-expressing ionocytes mutually cooperate to adjust Na+ uptake, which is analogous to the activity of the mammalian kidney. Cortisol is a hormone that controls Na+ uptake through regulating NCC expression and activity in mammals; however, cortisol-mediated control of NCC expression is little understood in non-mammalian vertebrates, such as teleosts. It is essential for our understanding of the evolution of such regulation to determine whether cortisol has a conserved effect on NCC in vertebrates. In the present study, we treated zebrafish embryos with low Na+ medium (LNa, 0.04 mM Na+) for 3 d to stimulate the mRNA expression of nhe3b, ncc, and cyp11b1 (a cortisol-synthesis enzyme) and whole body cortisol level. Exogenous cortisol treatment (20 mg/I, 3 d) resulted in an elevation of whole-body Na+ content, ncc expression, and the density of ncc-expressing cells in zebrafish larvae. In loss-of-function experiments, microinjection of glucocorticoid receptor (gr) morpholino (MO) suppressed sodium content, ncc expression, and the density of ncc-expressing cells, but injection of mr MO had no such effects. In addition, exogenous cortisol treatment and gr MO injection also altered ncc expression and the density of ncc-expressing cells in gcm2 morphant larvae. Taken together, cortisol and GR appear to regulate Na+ absorption through stimulating ncc expression and the differentiation of ncc-expressing ionocytes, providing new insights into the actions of cortisol on Na+ uptake. (C) 2015 Elsevier Ireland Ltd. All rights reserved.
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