High levels of plasma cortisol and impaired hypoosmoregulation in a mutant medaka deficient in P450c17I.
scl is a spontaneous medaka mutant deficient in P450c17I, which is required for production of sex steroids, but not of cortisol, the major role of which is osmoregulation in teleost fish. The scl mutant provides a new model to study the functions of these hormones. We first found that fish homozygous for this mutation have plasma cortisol constitutively at a high physiological level (1000 nM). Since we previously showed that this level reversed the seawater-type differentiation of the medaka gastrointestinal tract, hypoosmoregulation of the scl mutant was analyzed. Muscle water contents in freshwater were normal in scl homozygotes, but the contents were lower than those of the wild type (WT) after seawater transfer. There were no differences in gill mRNA levels of corticosteroid receptors or ion transporters between scl homozygotes and WT. In the intestine, expression of glucocorticoid receptors and Na(+)/K(+)/2Cl(-) cotransporter were induced in WT during seawater acclimation, but not in scl homozygotes. The high plasma cortisol may prevent hypoosmoregulation by inhibition of increased intestinal water absorption, essentially by the Na(+)/K(+)/2Cl(-) cotransporter, in seawater.
Department of Environmental Science, Faculty of Science, Niigata University, Ikarashi, Niigata, 950-2181, Japan; Ushimado Marine Institute, Faculty of Science, Okayama University, Ushimado, Setouchi, 701-4303, Japan.
Hideya
H
Takahashi
Department of Environmental Science, Faculty of Science, Niigata University, Ikarashi, Niigata, 950-2181, Japan.
Tadashi
T
Sato
Department of Bioscience, Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga, 526-0829, Japan.
Toshitaka
T
Ikeuchi
Ushimado Marine Institute, Faculty of Science, Okayama University, Ushimado, Setouchi, 701-4303, Japan.
Kazuhiro
K
Saito
Department of Environmental Science, Faculty of Science, Niigata University, Ikarashi, Niigata, 950-2181, Japan.
Mitsuru
M
Sakaizumi
Ushimado Marine Institute, Faculty of Science, Okayama University, Ushimado, Setouchi, 701-4303, Japan. Electronic address: ryu@uml.okayama-u.ac.jp.
Tatsuya
T
Sakamoto
D000818:Animals; D015971:Gene Expression Regulation, Enzymologic; D006854:Hydrocortisone / Q000097:blood*; D007413:Intestinal Mucosa / Q000378:metabolism; D017136:Ion Transport; D009132:Muscles / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D009990:Oryzias / Q000097:blood* / Q000235:genetics*; D064587:Osmoregulation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics* / Q000378:metabolism; D013256:Steroids / Q000378:metabolism; D014867:Water / Q000378:metabolism
D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D028021:Sodium-Potassium-Chloride Symporters; D013256:Steroids; D014867:Water; D013254:Steroid 17-alpha-Hydroxylase; D000254:Sodium-Potassium-Exchanging ATPase; D006854:Hydrocortisone
Cortisol; Glucocorticoid receptor; Intestine; Medaka; Mineralocorticoid receptor; Osmoregulation