Profiles of mRNA expression for prolactin, growth hormone, and somatolactin in Japanese eels, Anguilla japonica: The effect of salinity, silvering and seasonal change.

For understanding the functions of the growth hormone (GH)/prolactin (PRL)/somatolactin (SL) family of hormones, we examined pituitary mRNA expression of these hormones in anguillid eels in relation to salinity difference, silvering, and seasonal change. Female Japanese eels (Anguilla japonica) were collected in the brackish Hamana Lake and its freshwater rivers from July to December. To clarify the effect of salinity, the habitat use history of the eels were determined using otolith microchemistry. Expression levels of mRNA of each hormone were determined using real time PCR. Although GH and PRL have been known to be osmoregulatory hormones, there were no consistent differences in expression levels of these hormones between different salinity habitats. In contrast, SL mRNA expression was higher in eels from freshwater rivers than from the brackish lake. GH mRNA expression clearly decreased during silvering, whereas PRL and SL mRNA expression did not change. We also showed that PRL mRNA and SL mRNA decreased in the brackish lake and PRL mRNA increased in freshwater rivers from autumn to early winter. These findings provide basic knowledge for a further understanding of the role of these hormones.

[1]  K. Aida,et al.  Effects of growth hormone and cortisol on the downstream migratory behavior in masu salmon, Oncorhynchus masou. , 2007, General and comparative endocrinology.

[2]  W. Tzeng,et al.  Salinity preference of silvering Japanese eel Anguilla japonica: evidence from pituitary prolactin mRNA levels and otolith Sr:Ca ratios , 2003 .

[3]  K. Tsukamoto,et al.  11-ketotestosterone Synchronously Induces Oocyte Development and Silvering-Related Changes in the Japanese Eel, Anguilla japonica , 2012, Zoological science.

[4]  S. Kakizawa,et al.  Activation of somatolactin cells in the pituitary of the rainbow trout Oncorhynchus mykiss by low environmental calcium. , 1993, General and comparative endocrinology.

[5]  P. Lokman,et al.  Gonad histology and plasma steroid profiles in wild New Zealand freshwater eels (Anguilla dieffenbachii and A. australis) before and at the onset of the natural spawning migration. I. Females* , 2004, Fish Physiology and Biochemistry.

[6]  T. Kaneko,et al.  ROLE OF PROLACTIN AND SOMATOLACTIN IN CALCIUM REGULATION IN FISH , 1993 .

[7]  B. Björnsson.  The biology of salmon growth hormone: from daylight to dominance , 1997, Fish Physiology and Biochemistry.

[8]  D. Power,et al.  Quantification of Prolactin (PRL) and PRL Receptor Messenger RNA in Gilthead Seabream (Sparus aurata) after Treatment with Estradiol-17β1 , 2003, Biology of reproduction.

[9]  R. Nishioka,et al.  Osmoregulatory actions of growth hormone and prolactin in an advanced teleost. , 1997, General and comparative endocrinology.

[10]  A. Murk,et al.  Endocrine profiles during silvering of the European eel (Anguilla anguilla L.) living in saltwater , 2007 .

[11]  Sylvie Dufour,et al.  The silvering process of Anguilla anguilla: a new classification from the yellow resident to the silver migrating stage , 2005 .

[12]  T. Kaneko,et al.  Cell biology of somatolactin. , 1996, International review of cytology.

[13]  Hiroshi Kawauchi,et al.  The dawn and evolution of hormones in the adenohypophysis. , 2006, General and comparative endocrinology.

[14]  W. Dickhoff,et al.  Somatolactin stimulates in vitro gonadal steroidogenesis in coho salmon, Oncorhynchus kisutch. , 1992, General and comparative endocrinology.

[15]  Michael J. Miller,et al.  Deep-ocean origin of the freshwater eels , 2010, Biology Letters.

[16]  Chih-Wei Chang,et al.  Synchronous changes of morphology and gonadal development of silvering Japanese eel Anguilla japonica , 2003 .

[17]  H. Bern,et al.  Smoltification and seawater adaptation in coho salmon (Oncorhynchus kisutch): plasma prolactin, growth hormone, thyroid hormones, and cortisol. , 1989, General and comparative endocrinology.

[18]  K. Yamauchi,et al.  Immunohistochemical changes in production of pituitary hormones during artificial maturation of female Japanese eel Anguilla japonica , 2007, Fisheries Science.

[19]  K. Tsukamoto,et al.  Dynamics of Reproductive Hormones During Downstream Migration in Females of the Japanese Eel, Anguilla japonica , 2011, Zoological science.

[20]  S. McCormick,et al.  Prolactin and growth hormone in fish osmoregulation. , 2006, General and comparative endocrinology.

[21]  María del Pilar Martín del Río,et al.  Osmoregulatory action of PRL, GH, and cortisol in the gilthead seabream (Sparus aurata L). , 2002, General and comparative endocrinology.

[22]  G. Martínez‐Rodríguez,et al.  Gene and protein expression for prolactin, growth hormone and somatolactin in Sparus aurata: seasonal variations. , 2009, Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology.

[23]  R. Nishioka,et al.  Effects of thyroxine, growth hormone and cortisol on salinity preference of juvenile coho salmon (Oncorhynchus kisutch) , 1990 .

[24]  D. Power.  Developmental ontogeny of prolactin and its receptor in fish. , 2005, General and comparative endocrinology.

[25]  S. Dufour,et al.  Endocrine Evidence that Silvering, a Secondary Metamorphosis in the Eel, Is a Pubertal Rather than a Metamorphic Event , 2006, Neuroendocrinology.

[26]  W. Dickhoff,et al.  The role of growth in endocrine regulation of salmon smoltification , 1997, Fish Physiology and Biochemistry.

[27]  K. Limburg,et al.  Phenotypic plasticity of habitat use by three temperate eel species, Anguilla anguilla, A. japonica and A. rostrata , 2006 .

[28]  T. Yada,et al.  Changes in prolactin mRNA levels during downstream migration of the amphidromous teleost, ayu Plecoglossus altivelis. , 2010, General and comparative endocrinology.

[29]  S. Kaushik,et al.  Nutritional assessment of somatolactin function in gilthead sea bream (Sparus aurata): concurrent changes in somatotropic axis and pancreatic hormones. , 2004, Comparative biochemistry and physiology. Part A, Molecular & integrative physiology.

[30]  J. Johnsson,et al.  Dominance, Nutritional State, and Growth Hormone Levels in Rainbow Trout (Oncorhynchus mykiss) , 1996, Hormones and Behavior.

[31]  B. Mourot,et al.  Growth hormone (GH) and reproduction: a review , 1993, Fish Physiology and Biochemistry.

[32]  Lori A. Manzon.  The role of prolactin in fish osmoregulation: a review. , 2002, General and comparative endocrinology.

[33]  T. Ágústsson,et al.  Pituitary gene expression of somatolactin, prolactin, and growth hormone during Atlantic salmon parr–smolt transformation , 2003 .

[34]  Kaneko,et al.  Elevation of plasma somatolactin concentrations during acidosis in rainbow trout (Oncorhynchus mykiss) , 1996, The Journal of experimental biology.

[35]  J. Sumpter,et al.  Plasma somatolactin concentrations in salmonid fish are elevated by stress. , 1993, The Journal of endocrinology.

[36]  M. Rankin.  Endocrine Effects on Migration , 1991 .

[37]  Ishimatsu,et al.  Possible involvement of somatolactin in the regulation of plasma bicarbonate for the compensation of acidosis in rainbow trout , 1997, The Journal of experimental biology.

[38]  K. Tsukamoto,et al.  Facultative catadromy of the eel, Anguilla japonica, between freshwater and seawater habitats , 2001 .

[39]  D. Saito,et al.  Changes in expression of genes encoding gonadotropin subunits and growth hormone/prolactin/somatolactin family hormones during final maturation and freshwater adaptation in prespawning chum salmon , 2003, Endocrine.

[40]  K. Tsukamoto,et al.  Do all freshwater eels migrate? , 1998, Nature.

[41]  P. Prunet,et al.  Stimulation of parr-smolt transformation by hormonal treatment in Atlantic salmon (Salmo salar L.) , 1994 .

[42]  K. Tsukamoto,et al.  A silvering index for the Japanese eel Anguilla japonica , 2007, Environmental Biology of Fishes.

[43]  G. León,et al.  Prolactin gene expression and changes of prolactin pituitary level during the seasonal acclimatization of the carp. , 1994, Comparative biochemistry and physiology. Biochemistry and molecular biology.

[44]  H. Kawauchi,et al.  Somatolactin, a novel pituitary protein: purification and plasma levels during reproductive maturation of coho salmon. , 1992, The Journal of endocrinology.

[45]  S. Kakizawa,et al.  Changes in plasma somatolactin levels during spawning migration of chum salmon (Oncorhynchus keta) , 1995, Fish Physiology and Biochemistry.

[46]  J. Inoue,et al.  Evolution of the deep-sea gulper eel mitochondrial genomes: large-scale gene rearrangements originated within the eels. , 2003, Molecular biology and evolution.

[47]  J. Pérez-Sánchez,et al.  The involvement of growth hormone in growth regulation, energy homeostasis and immune function in the gilthead sea bream (Sparus aurata): a short review , 2000, Fish Physiology and Biochemistry.

[48]  E.,et al.  Chemistry and composition of fish otoliths : pathways , mechanisms and applications , 2006 .

[49]  P. Lokman,et al.  Gonad histology and plasma steroid profiles in wild New Zealand freshwater eels (Anguilla dieffenbachii and A. australis) before and at the onset of the natural spawning migration. II. Males , 1998, Fish Physiology and Biochemistry.

[50]  J. Mancera,et al.  Influence of cortisol, growth hormone, insulin-like growth factor I and 3,3′,5-triiodo-l-thyronine on hypoosmoregulatory ability in the euryhaline teleost Fundulus heteroclitus , 1999, Fish Physiology and Biochemistry.