TY - JOUR

T1 - Molecular characterization and expression of urotensin II and its receptor in the flounder (Platichthys flesus)

T2 - a hormone system supporting body fluid homeostasis in euryhaline fish

AU - Lu, Weiqun

AU - Greenwood, Michael

AU - Dow, Louise

AU - Yuill, Janette

AU - Worthington, John

AU - Brierley, Matthew J

AU - McCrohan, Catherine R

AU - Riccardi, Daniela

AU - Balment, Richard J

PY - 2006/8

Y1 - 2006/8

N2 - Urotensin II (UII) is a potent vasoconstrictor in mammals, but the source of circulating UII remains unclear. Investigations of the caudal neurosecretory system (CNSS), considered the major source of UII in fish, alongside target tissue expression of UII receptor (UT), can provide valuable insights into this highly conserved regulatory system. We report UII gene characterization, expression of the first fish UT, and responses to salinity challenge in flounder. The 12-aa UII peptide shares 73% sequence identity with pig and human UII. Flounder UT receptor shares 56.7% identity with rat. Although the CNSS is the major site of UII expression, RT-PCR revealed expression of UII and UT in all tissues tested. Around 30-40% of large CNSS Dahlgren cells expressed UII, alone or in combination with urotensin I and/or corticotrophin releasing hormone. Immunolocalization of UT in osmoregulatory tissues (gill, kidney) was associated with vascular elements. There were no consistent differences in CNSS UII expression or plasma UII between seawater (SW)- and freshwater (FW)-adapted fish, although gill and kidney UT expression was lower in FW animals. After acute transfer from SW to FW, plasma UII and kidney and gill UT expression were reduced, whereas UT expression in kidney was increased after reverse transfer. UII appears to be more important to combat dehydration and salt-loading in SW than the hemodilution faced in FW. Potentially, altered target tissue sensitivity through changes in UT expression, is an important physiological controlling mechanism, not only relevant for migratory fish but also likely conserved in mammals.

AB - Urotensin II (UII) is a potent vasoconstrictor in mammals, but the source of circulating UII remains unclear. Investigations of the caudal neurosecretory system (CNSS), considered the major source of UII in fish, alongside target tissue expression of UII receptor (UT), can provide valuable insights into this highly conserved regulatory system. We report UII gene characterization, expression of the first fish UT, and responses to salinity challenge in flounder. The 12-aa UII peptide shares 73% sequence identity with pig and human UII. Flounder UT receptor shares 56.7% identity with rat. Although the CNSS is the major site of UII expression, RT-PCR revealed expression of UII and UT in all tissues tested. Around 30-40% of large CNSS Dahlgren cells expressed UII, alone or in combination with urotensin I and/or corticotrophin releasing hormone. Immunolocalization of UT in osmoregulatory tissues (gill, kidney) was associated with vascular elements. There were no consistent differences in CNSS UII expression or plasma UII between seawater (SW)- and freshwater (FW)-adapted fish, although gill and kidney UT expression was lower in FW animals. After acute transfer from SW to FW, plasma UII and kidney and gill UT expression were reduced, whereas UT expression in kidney was increased after reverse transfer. UII appears to be more important to combat dehydration and salt-loading in SW than the hemodilution faced in FW. Potentially, altered target tissue sensitivity through changes in UT expression, is an important physiological controlling mechanism, not only relevant for migratory fish but also likely conserved in mammals.

KW - Adaptation, Physiological

KW - Amino Acid Sequence

KW - Animals

KW - Base Sequence

KW - Body Fluids

KW - Flounder

KW - Fresh Water

KW - Gene Expression Regulation

KW - Gene Library

KW - Gills

KW - Homeostasis

KW - Immunohistochemistry

KW - Kidney

KW - Molecular Sequence Data

KW - Pituitary Gland

KW - Receptors, G-Protein-Coupled

KW - Reverse Transcriptase Polymerase Chain Reaction

KW - Seawater

KW - Spinal Cord

KW - Urotensins

KW - Water-Electrolyte Balance

U2 - 10.1210/en.2005-1457

DO - 10.1210/en.2005-1457

M3 - Journal article

C2 - 16675528

VL - 147

SP - 3692

EP - 3708

JO - Clinical Endocrinology

JF - Clinical Endocrinology

SN - 0013-7227

IS - 8

ER -