Isolation and characterization of chum salmon growth hormone

Small GTPase control of pituitary hormone secretion: Evidence from studies in the goldfish (Carassius auratus) neuroendocrine model

The secretion of vertebrate pituitary hormones is regulated by multiple hypothalamic factors, which, while generally activating unique receptor systems, ultimately propagate signals through interacting intracellular regulatory elements to modulate hormone exocytosis. One important family of intracellular regulators is the monomeric small GTPases, a subset of which (Arf1/6, Rac, RhoA, and Ras) is highly conserved across vertebrates and regulates secretory vesicle exocytosis in many cell types. In this study, we investigated the roles of these small GTPases in basal and agonist-dependent hormone release from dispersed goldfish (Carassius auratus) pituitary cells in perifusion experiments. Inhibition of these small GTPases elevated basal LH and GH secretion, except for Ras inhibition which only increased basal LH release. However, variable responses were observed with regard to LH and GH responses to the two goldfish native gonadotropin-releasing hormones (GnRH2 and GnRH3). GnRH-dependent LH release, but not GH secretion, was mediated by Arf1/6 GTPases. In contrast, inhibition of Rac and RhoA GTPases selectively enhanced GnRH3- and GnRH2-dependent GH release, respectively, while Ras inhibition only enhanced GnRH3-evoked LH secretion. Together, our results reveal novel divergent cell-type- and ligand-specific roles for small GTPases in the control of goldfish pituitary hormone exocytosis in unstimulated and GnRH-evoked release.

Development of a giant grouper Luteinizing Hormone (LH) Enzyme-Linked Immunosorbent Assay (ELISA) and its use towards understanding sexual development in grouper

A recombinant giant grouper Luteinizing Hormone (LH) consisting of tethered beta and alpha subunits was produced in a yeast expression system. The giant grouper LH β-subunit was also produced and administered to rabbits for antibody development. The recombinant LH and its antibody were used to develop an Enzyme Linked Immunosorbent Assay (ELISA). This ELISA enabled detection of plasma LH levels in groupers at a sensitivity between 391 pg/ml and 200 ng/ml. Different species of grouper were assayed with this ELISA in conjunction with gonadal histology and body condition data to identify links between circulating LH levels and sexual development. We found that circulating levels of LH decreased when oocytes began to degenerate, and sex-transition gonadal characteristics were apparent when LH levels decreased further. When circulating LH levels were related to body condition (body weight/ body length), transitioning-stage fish had relatively high body condition but low plasma LH levels. This observation was similar across multiple grouper species and indicates that plasma LH levels combined with body condition may be a marker for early male identification in the protogynous hermaphrodite groupers.

Effects of recombinant salmon type II growth hormone and bovine growth hormone on growth of coho salmon (Oncorhynchus kisutch)

A comparison of the efficacy of salmon and bovine growth hormone to stimulate growth of coho salmon juveniles was performed. Oncorhynchus nerka (sockeye salmon) type II growth hormone (nGH2) was produced using a bacterial expression system, yielding approximately 25 mg of refolded recombinant protein per litre of cells. The purified nGH2 and bovine growth hormone (bGH) were tested in juvenile O. kisutch (coho salmon) over 24 weeks. Weekly intraperitoneal injections of 0.1 and 0.5 μg/g nGH2 resulted in a dose-dependent increase in weight and fork length compared to control fish injected with bovine serum albumin (BSA). Application of 0.5 μg/g bGH resulted in the same stimulation of growth as did 0.5 μg/g nGH2, indicating these proteins were equipotent. Following 6 weeks of treatment and a subsequent rest period of 7 weeks, coho salmon were further treated with bGH at 0.5 μg/g. A prior treatment with bGH did not reduce growth-promoting activity of bGH in subsequent treatments. Throughout the experiment, condition factor decreased at similar rates for all treatment groups. These data show that bGH, which is widely available, can be used to elevate growth rate in juvenile salmon comparably to homologous GH, and validate the use of bGH in physiological or ecological experiments where rapid growth is desired compared to that seen in wild type.

Effects of different green light intensities on the growth performance and endocrine properties of barfin flounder Verasper moseri

We previously reported that the somatic growth of barfin flounder, Verasper moseri, was effectively stimulated by the green light compared to the blue and red lights. Herein, we report the effects of different green light intensities on the growth and endocrine system of the fish. Fish were reared in a dark room with light from a light-emitting diode (LED) at a peak wavelength of 518nm under controlled photoperiod (10.5:13.5h, light:dark cycle; 06:00-16:30, light) with three levels of photon flux density (PFD)-2 (low), 7 (medium), or 21 (high) μmol·m^-2·s^-1 at the water surface. The average water temperature was 10.2°C, and the fish were fed until satiety. The fish reared under high PFD of green light showed the highest specific growth rates, followed by the medium PFD group. Under high PFD, the fish showed the highest amount of melanin-concentrating hormone mRNA in their brains and insulin in plasma, while the lowest amount of growth hormone was observed in their pituitary glands. These results suggest that the green light stimulated the growth of barfin flounders in a light intensity-dependent manner in association with their central and peripheral endocrine systems. However, when the fish were reared in an ordinary room where they received both ambient and green LED lights, the fish under LED and ambient light grew faster than those under ambient light only (control). Moreover, no difference was observed in the specific growth rate of the fish reared under the three different green LED light intensities, suggesting that the growth was equally stimulated by the green light within a certain range of intensities under ambient light.

Chronic effects of light irradiated from LED on the growth performance and endocrine properties of barfin flounder Verasper moseri

We investigated the effects of specific wavelengths of light on the growth of barfin flounder. The fish, reared in white tanks in a dark room, were irradiated with light from light-emitting diodes (LEDs) with peak wavelengths of 464nm (blue), 518nm (green), and 635nm (red) under a controlled photoperiod (10.5:13.5, light-dark cycle; 06:00-16:30, light). Fish were reared for four weeks in three independent experiments at three different water temperatures (averages of 14.9°C, 8.6°C, and 6.6°C). The fish irradiated with blue and green light had higher specific growth rates (% body weight⋅day(-1)) than fish irradiated with red light. Notably, green light had the greatest effect on growth among the three light wavelengths at 6.6°C. In the brains of fish reared at 6.6°C, the amounts of melanin-concentrating hormone 1 mRNA under green light were lower than those under red light, and amounts of proopiomelanocortin-C mRNA under blue and green light were higher than those under red light. No differences were observed for other neuropeptides tested. In the pituitary, no difference was observed in growth hormone mRNA content. In plasma, higher levels of insulin and insulin-like growth factor-I were observed in fish under green light than those of fish under red light. These results suggest that the endocrine systems of barfin flounder are modulated by a specific wavelength of light that stimulates somatic growth.

Effect of gonadotropin-releasing hormone on phagocytic leucocytes of rainbow trout

To clarify the role of gonadotropin-releasing hormone (GnRH) in the fish immune system, in vitro effect of GnRH was examined in phagocytic leucocytes of rainbow trout (Oncorhynchus mykiss). Gene expression of GnRH-receptor was detected by RT-PCR in leucocytes from head kidney. Administration of sGnRH increased proliferation and mRNA levels of a proinflammatory cytokine, tumor necrosis factor (TNF)-α, in trout leucocytes. Superoxide production in zymosan-stimulated phagocytic leucocytes was also increased by sGnRH in a dose-related manner from 0.01 to 100 nM. There was no significant effect of sGnRH on mRNA levels of growth hormone (GH) expressed in trout phagocytic leucocytes. Immunoneutralization of GH by addition of anti-salmon GH serum into the medium could not block the stimulatory effect of sGnRH on superoxide production. These results indicate that GnRH stimulates phagocytosis in fish leucocytes through a GnRH-receptor-dependent pathway, and that the effect of GnRH is not mediated through paracrine GH in leucocytes.

Immunocytochemical identification of adenohypophyseal cells in the pirarucu (Arapaima gigas), an Amazonian basal teleost

The adenohypophysis (AH) of juvenile pirarucu (Arapaima gigas), a representative species of the Osteoglossomorpha (bonytongue fishes, one of the oldest living groups of the teleosts), was studied using histochemical and immunocytochemical methods. The AH is comprised of the pars distalis (PD), without a clear distinction between rostral pars distalis (RPD) and proximal pars distalis (PPD), and the pars intermedia (PI). The neurohypophysis (NH) is positioned on top of the PD and penetrates and branches into the PI. In the most rostral dorsal portion of the PD, adrenocorticotropic cells and fusiform gonadotropic cells were found. In the central PD, scarce prolactin-producing cells and growth-hormone-producing cells were located mainly in the dorsal part, whereas round gonadotropic cells were abundant in the ventral portion of this region. Human thyrotropin immunoreactive cells were not found in the entire AH. In the PI, melanotropic, some adrenocorticotropic, and somatolactin-producing cells were located intermingled surrounding the neurohypophyseal branches. Our results showed that the A. gigas pituitary has some basal characteristics between the ancient Actinopterygii and the more derived teleosts.

A systematic immunohistochemical survey of the distribution patterns of GH, prolactin, somatolactin, beta-TSH, beta-FSH, beta-LH, ACTH, and alpha-MSH in the adenohypophysis of Oreochromis niloticus, the Nile tilapia

Fish pituitary plays a central role in the control of growth, development, reproduction and adaptation to the environment. Several types of hormone-secreting adenohypophyseal cells have been characterised and localised in diverse teleost species. The results suggest a similar distribution pattern among the species investigated. However, most studies deal with a single hormone or hormone family. Thus, we studied adjacent sections of the pituitary of Oreochromis niloticus, the tilapia, by conventional staining and immunohistochemistry with specific antisera directed against growth hormone (GH), prolactin (PRL), somatolactin (SL), thyrotropin (beta-TSH), follicle-stimulating hormone (beta-FSH), luteinising hormone (beta-LH), adrenocorticotropic hormone (ACTH) and melanocyte-stimulating hormone (alpha-MSH). The pituitary was characterised by a close interdigitating neighbourhood of neurohypophysis (PN) and adenohypophysis. PRL-immunoreactive and ACTH-immunoreactive cells were detected in the rostral pars distalis. GH-immunoreactive cells were present in the proximal pars distalis (PPD). A small region of the PPD contained beta-TSH-immunoreactive cells, and beta-LH-immunoreactive cells covered approximately the remaining parts. Centrally, beta-FSH-immunoreactive cells were detected in the vicinity of the GH-containing cells. Some of these cells also displayed beta-LH immunoreactivity. The pars intermedia was characterised by branches of the PN surrounded by SL-containing and alpha-MSH-immunoreactive cells. The ACTH and alpha-MSH antisera were observed to cross-react with the respective antigens. This cross-reactivity was abolished by pre-absorption. We present a complete map of the distinct localisation sites for the classical pituitary hormones, thereby providing a solid basis for future research on teleost pituitary.

Production, characterization and applications of mouse anti-grass carp (Ctenopharyngodon idellus) growth hormone monoclonal antibodies

Mouse anti-grass carp growth hormone (gcGH) monoclonal antibody (MAb) secretors were produced by PEG-mediated fusion of NS-1 myeloma cells and splenic B-lymphocytes of gcGH hyper-immunized mice. Positive secretors were screened by direct ELISA and cloned by limiting dilution. Three positive secretors, 21D3, 22G5 and 23B3, were obtained in a single fusion trial. Anti-gcGH MAbs were produced by growing hybridomas in the peritoneal cavity of pristane-primed mouse. The three MAbs were isotyped to be IgG2a, IgG2b and IgM, respectively. IgG MAbs were purified from ascitic fluid by Hitrap protein G column and IgM MAb was purified by gel filtration chromatography. The purified MAbs were highly specific and had moderate binding affinity. The MAbs were successfully used for the purification of native gcGH from mature grass carp pituitary extract by one-step immunoaffinity chromatography, for the quantification of gcGH by competitive sandwich ELISA, and for the probing of somatotropes in grass carp pituitary by immunohistochemistry.

Pituitary adenylate cyclase-activating polypeptide (PACAP)-like immunoreactivity in the brain of a teleost, Uranoscopus japonicus: immunohistochemical relationship between PACAP and adenohypophysial hormones

The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) could play a role in stimulating pituitary hormone release in fish brain. In this study, we used immunochemical techniques to examine the histological and quantitative distribution of PACAP in the central nervous system (CNS) of a teleost, the stargazer, Uranoscopus japonicus. In addition, high performance liquid chromatographic (HPLC) analysis was performed to characterize the form of PACAP present, while the relationship between PACAP and adenohypophysial hormones was also determined immunohistochemically. PACAP-like immunoreactive (LI) neuronal cell bodies and fibers were found not only in the hypothalamo-pituitary region but also in the midbrain and hindbrain regions. PACAP-LI fibers were identified in the neurohypophysis in close proximity to pituitary cells containing immunoreactive hormones such as somatolactin, the N-terminal peptide of proopiomelanocortin, and N-acetyl endorphin. The concentration of immunoreactive PACAP in whole brain tissue was approximately 300 pmol/g wet weight. The average concentrations of immunoreactive PACAP in regions of the telencephalon, diencephalon, tectum, cerebellum, and rhombencephalon were 217.53, 510.26, 83.30, 148.64, and 364.62 pmol/g, respectively. In reverse-phase HPLC experiments, the predominant form of immunoreactive PACAP eluted closely with synthetic stargazer PACAP38, while PACAP27-like immunoreactivity was negligible. These results suggest that PACAP38 is the predominant PACAP form in the stargazer CNS, and that PACAP acts not only as a hypophysiotropic factor for adenohypophysial hormone release but also as a neurotransmitter and neuromodulator in the CNS.

Seasonal modulation of growth hormone mRNA and protein levels in carp pituitary: evidence for two expressed genes

Adaptation of eurythermal fish to naturally varying environmental conditions involves modulation of expressions of various factors in the hypothalamo-hypophyseal axis. Here we used three complementary approaches to assess the seasonal variation of growth hormone (GH) protein and mRNA levels in pituitary glands of acclimatized carp fish. First, a polyclonal antibody raised against an oligopeptide derived from the carp GH sequence was used for immunohistochemistry; second, oligonucleotides specific for GH transcripts were used for in situ hybridization. Specific immunodetection of GH coincides with visualization of GH mRNA in the proximal pars distalis, the specific location of somatotroph cells in carp pituitary gland. Finally, competitive RT-PCR analyses confirmed that GH expression exhibits seasonal cyclical reprogramming with higher levels in summer- than in winter-adapted fish. The expression pattern suggests an important role for GH in the molecular mechanisms underlying the acclimatization process. In parallel, amplification of sequences from the fourth intron and adjacent sites from exons IV and V demonstrates the existence of a new GH gene previously undescribed. The detection of transcripts corresponding to each gene suggests that both GH gene copies are active in the duplicated carp genome and that they are similarly affected by seasonal adaptation.

Immunohistochemical Observation of Pituitary Adenylate Cyclase–activating Polypeptide (PACAP) and Adenohypophysial Hormones in the Pituitary of a Teleost, Uranoscopus japonicus

A neuropeptide, pituitary adenylate cyclase-activating polypeptide (PACAP) has possible potency as a hypothalamic factor mediating the release of pituitary hormones, especially growth hormone (GH), in the fish pituitary. We used double-immunostaining to examine the relationship between PACAP nerve fibers and adenohypophysial hormone-producing cells in the pituitary of a teleost, the stargazer Uranoscopus japonicus, and enzyme immunoassay to determine the quantity of PACAP in the stargazer brain, in conjunction with the body mass and gonad somatic index (GSI) of fish. In adult stargazer, PACAP-like immunoreactive (PACAP-LI) nerve fibers and endings were identified in both the neurohypophysis and adenohypophysis in close proximity to pituitary cells containing immunoreactive hormones such as prolactin, somatolactin, the N-terminal peptide of proopiomelanocortin, and N-acetyl endorphin. PACAP-LI nerve fibers were also identified close to immunoreactive GH cells in the pituitary of young fish. The concentration of immunoreactive PACAP in whole brain ranged from 100 to 800 pmol/g wet weight, in fish with weighing 70-480 g. A negative correlation was found between the concentration of immunoreactive PACAP in the whole brain and body weight, but there was no relation between the former and GSI. These results suggest that PACAP may act as a hypophysiotropic factor in the stargazer pituitary.

Effects of prolactin and growth hormone on plasma levels of lysozyme and ceruloplasmin in rainbow trout

In vivo and in vitro effects of prolactin (PRL) and growth hormone (GH) on plasma levels of lysozyme and ceruloplasmin were examined in the rainbow trout (Oncorhynchus mykiss). Hypophysectomy had no effect on the plasma lysozyme level. Implantation of PRL- or GH-containing cholesterol pellets increased the lysozyme level in a dose-related manner. After hypophysectomy and sham operation, plasma ceruloplasmin was elevated above the level in intact fish, suggesting inflammation caused by the surgery. PRL or GH treatment significantly attenuated the increased level of ceruloplasmin in the operated fish. Expression of lysozyme mRNA was detected in the leucocytes isolated from the peripheral blood by RT-PCR. In vitro administration of PRL or GH showed no effect on the proliferation of isolated leucocytes or on the total protein content; however, lysozyme activity in the medium increased in a dose-related manner. These results suggest that PRL and GH directly stimulate lysozyme production without affecting the proliferation of leucocytes, and the attenuated ceruloplasmin level increased in response to inflammation.

Effects of prolactin and growth hormone on proliferation and survival of cultured trout leucocytes

The in vitro effects of prolactin (PRL) and growth hormone (GH) on the proliferation and survival of leucocytes isolated from the blood of the rainbow trout (Oncorhynchus mykiss) were examined, with special reference to the immunosuppression by cortisol. Both PRL and GH induced a mitogenic effect in trout leucocytes. Contrary, the frequencies of annexin V-positive apoptotic cells and propidium iodide-positive dead cells were decreased by the administration of PRL, but were uninfluenced by GH. Administration of cortisol suppressed the mitotic activity and induced cell death of leucocytes. PRL inhibited the decrease in mitosis and the increase in cell death due to cortisol. GH significantly assisted recovery of cortisol-suppressed mitosis but did not influence the survival of leucocytes. These results suggest that PRL and GH are involved in the maintenance of specific immune functions in fish through a prevention of immunosuppression by cortisol.

FSH and LH-beta subunits in the preoptic nucleus: ontogenic expression in teleost

In the present study we cloned, sequenced, and confirmed the presence of mRNAs of gonadotropins (FSH-beta, LH-beta subunits) from the brain and pituitary of tilapia, Oreochromis niloticus. Further, we examined the spatio-temporal expression pattern of FSH-beta and LH-beta in the brain and pituitary of two species of teleost (tilapia, O. niloticus; sockeye salmon, Oncorhynchus nerka), using in situ hybridization and immunological methods. The expression of FSH and LH immunoreactivity appeared simultaneously in the brain and pituitary (tilapia, 14 days; sockeye, 51 days after fertilization). In the pituitary, FSH mRNA and peptide expressing cells were distinct from LH expressing cells located in the ventral proximal pars distalis. In the brain, FSH and LH immunoreactivity was co-localized in cells of the preoptic nucleus parvocellularis, magnocellularis, and gigantocellularis. Fibers immunoreactive to FSH and LH antisera were seen along the forebrain-hypothalamus and in the neurohypophysis of the pituitary. Double-label immunofluorescence revealed FSH and LH immunoreactivity co-localized in arginine vasotocin synthesizing preoptic neurons. Our results show that FSH and LH-producing cells have developmental origins in the brain as well as in the pituitary. In addition, we propose that the brain-derived gonadotropins may function as hypophysiotropic hormones that regulate pituitary cells and along with arginine vasotocin could act as neuromodulators of reproductive behaviors.

Immunocytochemical characterization of adenohypophyseal cells in the greater weever fish (Trachinus draco)

The adenohypophysis of the greater weever fish (Trachinus draco) was studied using histochemical and immunocytochemical methods. The adenohypophysis comprised the rostral pars distalis (RPD), the proximal pars distalis (PPD), and the pars intermedia (PI). Neurohypophysis showed a patent hypophyseal stalk which was divided into several branches intermingled with the adenohypophysis. Salmon prolactin (PRL)-immunoreactive (ir) cells, arranged in follicles, resided in the RPD and the most rostral part of the ventral PPD. Human adrenocorticotropin (ACTH)-ir cells were located in the RPD between PRL-ir cells and the neurohypophyseal processes. Salmon and seabream somatotropin (GH)-ir cells were located in both the dorsal and the ventral PPD. Some GH-ir cells were seen in surrounding and in contact with neurohypophyseal branches, whereas other isolated or clustered GH-ir cells were embedded in adenohypophyseal cells of the PPD. In addition, isolated or clustered GH-ir cells were also detected in the tissue of the PPD covering the most rostral part of PI. Only one class of salmon and carp gonadotropin (GTH)-ir cells was detected. Isolated or clustered GTH-ir cells resided in both the dorsal and the ventral PPD and were seen surrounding the PI and in the tissue of the PPD covering the most rostral part of PI. In addition, a few scattered GTH-ir cells were observed in the ventral RPD. Scattered groups of thyrotropin (TSH)-ir cells were present in the anteroventral PPD. Salmon and seabream somatolactin (SL)-ir and bovine melanotropin (MSH)-ir cells were intermingled surrounding the neurohypophyseal tissue. SL-ir cells were negative to periodic acid-Schiff technique. MSH-ir cells showed a very weak immunoreactivity to anti-human ACTH((1-24)) serum. In addition to the PI location, few isolated or clustered SL- and MSH-ir cells were observed in the dorsal PPD.

Spatio-temporal expression of gonadotropin-releasing hormone receptor subtypes in gonadotropes, somatotropes and lactotropes in the cichlid fish

The description of two or more forms of gonadotropin-releasing hormone (GnRH) in most vertebrates suggests multiple roles for this family of peptide hormones. In order to verify these functions, we analysed the anatomical location, time of initial expression and ontogenic changes in three distinct GnRH receptors (GnRH-Rs) in developing and sexually mature tilapia, using antisera raised against the extracellular loop three of the receptor, which is a determinant in ligand-selectivity and receptor coupling to signalling pathways. In all age groups, including males and females, using in situ hybridization and double-label immunological methods, GnRH-R type IA was colocalized in cells containing luteinizing hormone (LH) beta-subunit in the pituitary. GnRH-R type IB was visualized in prolactin cells and LH cells. The type III GnRH-R was expressed in growth hormone cells. On day 8 after fertilization, GnRH-R type III was first seen in growth hormone cells and, subsequently, on day 15, GnRH-Rs type IA and type IB were first seen in LH and prolactin cells, respectively. On day 25, the receptor occupied area per pituitary and the staining intensity of GnRH-R type IA increased significantly, consistent with the hypothesis that differentiation of GnRH neurones and their inputs to the pituitary coincide precisely with gonadal sex differentiation and steroidogenesis in tilapia. The differential distribution of GnRH-Rs in the pituitary provides the first clear evidence that the three native GnRH variants in tilapia have cognate receptors, each capable of regulating different pituitary endocrine cells.

Differential secretion of chicken growth hormone variants after growth hormone-releasing hormone stimulation in vitro

Variants of growth hormone (GH) are present in most vertebrates. Chicken GH (cGH) undergoes posttranslational modifications that contribute to its structural diversity. Although the 22-kDa form of GH is the most abundant, some other variants have discrete bioactivities that may not be shared by others. The proportion of cGH variants changes during ontogeny, suggesting that they are regulated differentially. The effect of growth hormone-releasing hormone (GHRH) on the release of cGH variants was studied in both pituitary gland and primary cell cultures, employing sodium dodecyl sulfate polyacrylamide gel electrophoresis, Western blotting, and densitometry. GHRH (2 nM, 2 h) stimulated the secretion of most of the size variants of cGH although the amplitude of increase was not equal for each one. A differential effect on the secretion of GH size variants, particularly on the 22- (monomer) and 26-kDa (putatively glycosylated) cGH isoforms was found in both systems. In the whole pituitary culture, the proportion of the 26-kDa immunoreactive cGH increased 35% while the 22 kDa decreased 31% after GHRH treatment in comparison with the controls. In the primary cell culture system, the proportion of the glycosylated variant increased 43% whereas the monomer and the dimer decreased 22.26 and 29%, respectively, after GHRH stimulation. Activators of intracellular signals such as 1 mM 8-bromo-cAMP and 1 microM phorbol myristate acetate had a similar effect to that obtained with GHRH. The data support the hypothesis that GH variants may be under differential control and that GHRH promotes the release of a glycosylated cGH variant that has an extended half-life in circulation.

Stimulation of non-specific immune functions in seawater-acclimated rainbow trout, Oncorhynchus mykiss, with reference to the role of growth hormone

The influence of acclimation to seawater (SW) and growth hormone (GH) administration on immune functions was examined in the rainbow trout (Oncorhynchus mykiss). After 3 days acclimation to dilute SW (12 parts per thousand, ppt), an increase in plasma lysozyme activity was observed compared to the fish kept in fresh water (FW). No change was seen in plasma immunoglobulin M (IgM) levels. When they were transferred from dilute SW to full-strength SW (29 ppt) after a single intra-peritoneal injection of ovine or salmon GH, plasma sodium levels of GH-treated fish were significantly lower than those of the control fish injected with Ringer's solution 24 h after the transfer. The plasma level of IgM was not influenced by GH injection in the fish kept in FW nor in those transferred to SW. The administration of GH increased plasma lysozyme activity in the fish in FW, but no further increase was seen after SW transfer. The production of superoxide anions in peripheral blood leucocytes was stimulated by GH in both FW and SW. These results suggest that GH is involved in the stimulation of the non-specific immune functions in SW-acclimated salmonids.

An immunocytochemical study of the pituitary gland of the white seabream (Diplodus sargus)

The adenohypophysis of the white seabream (Diplodus sargus) was studied using histochemical and immunocytochemical techniques. The adenohypophysis was composed of rostral pars distalis, proximal pars distalis and pars intermedia. Prolactin (anti-chum salmon prolactin positive) and adrenocorticotropic (anti-human ACTH positive) cells were found in the rostral pars distalis. Prolactin cells were organized into follicles, while ACTH cells were arranged in cords around neurohypophyseal tissue branches that penetrated the rostral pars distalis. In the proximal pars distalis, somatotropic (anti-chum salmon and anti-gilthead seabream growth hormone positive), gonadotropic (anti-chum salmon beta-gonadotrophin II and anti-carp beta-gonadotrophin II positive, but anti-chum salmon beta-gonadotrophin I negative) and thyrotropic (anti-human beta-thyrotropin positive) cells were observed. Growth hormone cells were restricted to the dorsal and ventral part of the proximal pars distalis. They were clustered or surrounded the neurohypophyseal branches. Only one type of gonadotrophin cell was identified and they were clustered or isolated in the proximal pars distalis. Scattered groups of thyrotropin cells were located throughout the proximal pars distalis. In the pars intermedia somatolactin (anti-chum salmon and anti-gilthead seabream somatolactin positive) and melanotropic (anti-alpha-melanotropic hormone positive) cells were localized. In addition, gonadotrophin cells surrounded the pars intermedia or distributed evenly between somatolactin and melanotropic hormone cells. Somatolactin cells were periodic acid-Schiff negative and surrounded the neurohypophyseal branches intermingled with melanotropic cells. These cells were also immunoreactive to anti-human ACTH antiserum.

Isolation, cDNA cloning, and growth promoting activity of rabbitfish (Siganus guttatus) growth hormone

We report the isolation, cDNA cloning, and growth promoting activity of rabbitfish (Siganus guttatus; Teleostei; Perciformes; Siganidae) growth hormone (GH). Rabbitfish GH was extracted from pituitary glands under alkaline conditions, fractionated by gel filtration chromatography on Sephadex G-100, and purified by high-performance liquid chromatography. The fractions containing GH were identified by immunoblotting with bonito GH antiserum. Under nonreducing conditions, the molecular weight of rabbitfish GH is about 19 kDa as estimated by SDS-PAGE. The purified hormone was potent in promoting growth in rabbitfish fry. Weekly intraperitoneal injections of the hormone significantly accelerated growth. This was evident 3 weeks after the start of the treatment, and its effect was still significant 2 weeks after the treatment was terminated. Rabbitfish GH cDNA was cloned to determine its nucleotide sequence. Excluding the poly (A) tail, rabbitfish GH cDNA is 860 base pairs (bp) long. It contained untranslated regions of 94 and 175 bp in the 5' and 3' ends, respectively. It has an open reading frame of 588 bp coding for a signal peptide of 18 amino acids and a mature protein of 178 amino acid residues. Rabbitfish GH has 4 cysteine residues. On the amino acid level, rabbitfish GH shows high identity (71-74%) with GHs of other perciforms, such as tuna, sea bass, yellow tail, bonito, and tilapia, and less (47-49%) identity with salmonid and carp GHs.

Purification, characterization, and bioassay of prolactin and growth hormone from temperate basses, genus Morone

Prolactin (PRL) and two variants of growth hormone (GH), purified from pituitaries of striped bass (Morone saxatilis) and its hybrid with white bass (M. saxatilis x M. chrysops) by gel filtration chromatography under alkaline conditions followed by reversed-phase high pressure liquid chromatography, appear similar between species. Both the minor (GH I) and the major (GH II) forms of purified GH appeared as single bands (M(r) approximately 23,000) after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, as did the purified PRL (M(r) approximately 24,000). The molecular weights of GH II and PRL determined by MALDI TOF mass spectroscopy were 21.2 and 21.3 kDa, respectively. In Western blotting experiments, an antiserum against tilapia (Oreochromis mossambicus) 24K PRL specifically recognized Morone PRL, while an antiserum against tilapia GH specifically recognized Morone GH I and II. Chemical identities of the putative PRL and GH I were further confirmed by N-terminal peptide sequencing, while internal sequence analysis was performed on GH II because it was blocked at its N-terminus. Over a stretch of 29 amino acids, Morone PRL was found to be 76% identical to tilapia 24K PRL, 72% identical to tilapia 20K PRL, 72% identical to chum salmon (Oncorhynchus keta) PRL I, and 69% identical to eel (Anguilla japonica) PRL I. Alignment of the hybrid striped bass GH sequences with those of several other advanced marine teleosts indicated 75-85% sequence identity for GH I (40 amino acids) and 95-98% identity for GH II (45 amino acids). Biological activity of striped bass GH II was confirmed using a heterologous in vitro assay of insulin-like growth factor I mRNA production by coho salmon (On. kisutch) hepatocytes. An in vivo bioassay, involving hypophysectomy of hybrid striped bass and treatment of the fish maintained in fresh water with homologous PRL, confirmed that the purified striped bass PRL was also bioactive.

Effects of prolactin and growth hormone on plasma immunoglobulin M levels of hypophysectomized rainbow trout, Oncorhynchus mykiss

Immunoglobulin M (IgM) is a major component of the humoral immune system of teleosts. This study examines the effects of hypophysectomy and subsequent replacement with prolactin (PRL) or growth hormone (GH) upon the plasma IgM levels of the rainbow trout (Oncorhynchus mykiss). Plasma IgM levels of the hypophysectomized fish were decreased to 30% of those in sham-operated fish 1 or 4 weeks after operation. Implantation of a cholesterol pellet containing salmon PRL or GH restored plasma IgM levels of the hypophysectomized fish, suggesting important roles for PRL and GH in the regulation of circulating IgM level in trout.

Growth hormone, sexual maturity and steroids in male carp (Cyprinus carpio)

Samples of pituitary, blood plasma and gonad were taken from male carp. The growth hormones (GH) in the pituitary and plasma were measured in fish of various body weights (BW) and degrees of gonad development, and compared with the levels of 17 beta-estradiol (E2), testosterone (T), 17 alpha-hydroprogesterone (17-P), 11-ketotesterone (11-KT) and progesterone (P) in the testes and plasma. The gonadosomatic index increased rapidly with BW from 100 to 600 g, and then decreased at 900 g. The pituitary GH did not change with BW, but plasma GH was higher in fish weighing 300 +/- 50 and 600 +/- 50 g, than in fish weighing 900 +/- 50 g. In fish weighing 150 +/- 50 to 300 +/- 50 g, the level of T rose significantly in the testes (2.27 ng g-1) and plasma (1.3 ng g-1); E2 was very low in both testes (0-30 pg g-1) and plasma (11-28 pg ml-1), increasing as BW rose from 150 to 600 g. The level of P rose mainly at BW of 300 +/- 50 and 600 +/- 50 g: from 0 to 25 ng g-1 in the testes and from 0 to 17 ng ml-1 in the plasma. The level 17-P rose from 2.5 to 20 ng g-1 in the testes at 600 +/- 50 g BW, but no significant change was recorded in the plasma. The level of 11-KT rose significantly in the tests of fish at 300, 600 and 900 g (0.5-6 ng g-1). The application of different steroids (E2, T and 17-P) on a primary culture of pituitary cells led to the release of GH. Release was significantly higher (P < 0.05) after 4 h at steroid concentrations of 10(-6) M.

Development of an ELISA for chum salmon (Oncorhynchus keta) growth hormone

A specific and sensitive enzyme-linked immunosorbent assay (ELISA) was developed for the measurement of low levels of serum growth hormone (GH) in chum salmon (Oncorhynchus keta). The antiserum to GH (a-rsGH) was obtained from a rabbit immunized with recombinant chum salmon GH. The noncompetitive ELISA was performed by a sandwich method using a-rsGH rabbit IgG as the first antibody, its biotinylated Fab' fragment as the second antibody, and the avidin-biotin reaction for signal amplification. This assay could be run in 3 days and routinely detected GH at concentrations as low as 0.5 ng/ml. The development of an ELISA for GH made possible quantification of serum GH levels. In this assay system, parallel dilution curves were obtained using purified chum salmon GH and GH's from several species of the genus Oncorhynchus.

Immunostimulating effect of growth hormone: in-vivo administration of growth hormone in rainbow trout enhances resistance to Vibrio anguillarum infection

In-vivo administration of purified (nGH) and recombinant (rGH) chum salmon, Oncorhynchus keta, growth hormone enhanced the survival of rainbow trout, O. mykiss, against virulent Vibrio anguillarum. Macrophages obtained from rainbow trout that were treated in vivo with either GH preparation showed enhanced stimulation of the chemiluminescent responses induced by opsonized V. anguillarum cells and increased phagocytic activities. However, the serum bactericidal activity against V. anguillarum was not enhanced in fish injected with nGH or rGH. These findings show that in-vivo administration of either GH preparation can effectively prime macrophages and increase the resistance to V. anguillarum in rainbow trout.

Growth hormone, gonad development, and steroid levels in female carp

The pituitary and plasma growth hormone (GH) levels of female carp (Cyprinus carpio L.) were measured in fish of various sizes and degrees of maturity, and were matched against the levels of 17 beta-estradiol (E2), testosterone (T), 17 alpha-hydroxyprogesterone (17-P), and progesterone (P) in the ovary and plasma. The short-term action of the above hormones and 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17,20-P) on the release of GH was examined in vitro in primary culture pituitary cells. The gonadosomatic index (%GSI) increased rapidly in specimens when they had attained 900 +/- 50 g body weight (BW). The pituitary and plasma GH levels increased between 150 and 600 g BW (when oocytes reached the stage at which lipoprotein appeared in the cytoplasm), but at 900 g BW (with oocytes in vitellogenesis) the plasma GH dropped, while pituitary GH remained high. E2 increased with BW, reaching its maximum at 600 and 900 g BW in the ovary and plasma, respectively. Similar patterns were found in the levels of T and P, both hormones reaching their maximum levels at 900 g BW. The level of 17-P was very low and did not increase in proportion to BW. The application of various concentrations of different steroids on a primary culture of pituitary cells led to release of GH. The highest degrees of release were obtained from 10(-6) and 10(-7) M E2, 10(-6) M T, 10(-7) M 17-P and 10(-8) M 17,20-P. In all these cases, hormone treatment effected higher release of GH than was found in the control. A model of the relationship between GH and the steroids associated with maturation is proposed.

Embryonic development of gonadotropin-releasing hormone neurons in the sockeye salmon

Immunocytochemistry and in situ hybridization were used to test the hypothesis that gonadotropin-releasing hormone (GnRH) neurons are formed in the olfactory placode during embryonic development in a salmonid, Oncorhynchus nerka. The development of GnRH neurons and the pituitary cell types was examined from 19 through 910 days after fertilization. Immunoreactive GnRH was first detected at 19 days in the cells of the olfactory placode. GnRH immunoreactivity was not detected in any other structure of the central nervous system at this age. By day 24, GnRH-immunoreactive neurons were seen in the apical, intermediate, and basal layers of the olfactory placode. From days 30 through 51, GnRH neurons were seen emerging from the epithelium, along the olfactory nerve, and at the rostral olfactory bulb. By day 41, GnRH immunoreactivity was lost in the nasal epithelium. In the 72-day-old fish, most of the GnRH neuronal population was found in ganglia of the nervus terminalis, at the cribriform bone (gCB), and at the rostral olfactory bulb (gROB). On day 293, a decrease in GnRH-immunoreactive neurons in the gCB and gROB was concomitant with an initial appearance of GnRH-immunoreactive neurons and fibers along the caudoventral olfactory bulb. By day 462, the distribution of GnRH neurons and fibers was almost similar to adults. In maturing adults (910 days), GnRH-immunoreactive neurons were rarely seen in the nasal regions, but were primarily found in the basal forebrain. GnRH fibers were widespread in the brain, proximal para distalis, and in the pars intermedia of the pituitary. Our study supports the notion that neurons expressing salmon-GnRH mRNA and peptide originate in the medial olfactory placode and migrate into the basal forebrain during development. The midbrain neurons did not express salmon-GnRH mRNA or peptide in the larval and juvenile fish.

Gonadotropin releasing hormone (GnRH) neurons project to growth hormone and somatolactin cells in the steelhead trout

Analysis of gene expression using gonadotropin-releasing hormone (GnRH) antisense oligonucleotide confirmed by immunocytochemical localization the occurrence of GnRH neurons along the nervus terminalis in the steelhead trout (Oncorhynchus mykiss). Double-label immunocytochemistry revealed the distribution of mammalian (m), salmon (s) and chicken II (cII)-type GnRHs and various pituitary hormones. Both sGnRH and mGnRH appeared to be colocalized in the same cells of the nervus terminalis. Chicken GnRH II-immunoreactivity was found only in fibers and terminals. In the younger fish [73 and 186 days after fertilization (DAF)] GnRH neurons were seen rostral to the olfactory bulb. A novel GnRH ganglion, along the nervus terminalis, was found at the cribiform bone (gCB). A few non-immunoreactive rounded cells were seen among the GnRH neurons. A second smaller ganglion was seen at the most rostrally located part of the ventromedial olfactory bulb (gROB). In the older fish (850 DAF) GnRH neurons were also observed in the basal forebrain. A small group of neurons (2-3 cells), at the caudoventromedial border of the olfactory bulb, formed the ganglion terminale. Occasionally isolated GnRH-immunoreactive cells were seen at the base of the olfactory epithelium, along the ventromedial margins of the olfactory nerve. GnRH-immunoreactive and GnRH mRNA expressing neurons were absent from midbrain regions at the ages observed. GnRH-immunoreactive fibers were present only in older fish. The pattern of distribution of fibers that were immunoreactive to all three forms of GnRH was identical. Fibers were seen along the medial side of the olfactory nerve, throughout the brain and in the pituitary, associated with growth hormone and somatolactin cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning of the sole (Solea senegalensis) growth hormone-encoding cDNA

We report here the complete nucleotide (nt) sequence of a cDNA clone encoding Solea senegalensis growth hormone (sGH) isolated from an expression library prepared from sole pituitary gland poly(A)+RNA. The library was screened using a flounder GH cDNA. The cDNA sequence containing an insert of 769 nt was found to encode a polypeptide of 203 amino acids (aa), including a signal peptide of 17 aa. The 5'- and 3'-untranslated regions of the message are 17 and 119-nt long, respectively. Northern blot hybridization detected a 0.9-kb RNA species. The sGH cDNA sequence shows homologies of 80.9, 76.9, 73.8 and 64.2% with the GH of tuna, gilthead seabream, flounder and rainbow trout.

Genomic structure of growth hormone genes in chinook salmon (Oncorhynchus tshawytscha): presence of two functional genes, GH-I and GH-II, and a male-specific pseudogene, GH-psi

Two chinook salmon (Oncorhynchus tshawytscha) growth hormone genes (a functional GH-I gene and a pseudogene, GH-psi) were isolated and characterized. The GH-I gene sequence consists of 1.9 kb of 5'-flanking sequence, 4.1 kb of transcribed region, and 64 bp of 3'-flanking sequence, and contains 6 exons and 5 introns. The pseudogene, GH-psi, spanning 4.1 kb, has a similar structure as the GH-I gene. However, it has one wrong splicing sequence at the intron 1/exon 2 junction, one premature termination codon in exon 5, and a deletion in the last half of exon 5 and the first part of intron 5. In addition to GH-I gene and GH-psi, a third GH gene, GH-II, was identified by the polymerase chain reaction (PCR) and subsequently shown to be the second functional GH-II gene. To study the linkage arrangement of these three GH genes, 50 unrelated chinook salmon (25 males and 25 females) and one chinook salmon family were analyzed by PCR. The results showed that GH-psi exists only in males and that it segregates from father to sons. These results suggest that GH-psi is sex specific and probably resides on the Y chromosome. Together these results indicate that there are three GH genes in the genome of male chinook salmon, and only two GH genes in the females. The extra GH gene in the male is, however, a pseudogene.

Lungfish prolactin exhibits close tetrapod relationships

This paper describes the isolation and the complete amino-acid sequence of prolactin (PRL) from the pituitary glands of African lungfish, Protoputerus aethiopicus. We purified the hormone from an alkaline extract of the pituitaries using a two-step chromatographic procedure by detecting specific immunoblot reactivity with rabbit antisera against salmon PRL. The lungfish PRL consists of 200 amino-acid residues. Sequence comparison revealed that the PRL shows 66% identities with amphibian, reptilian and bird PRLs, 57% with mammalian PRLs, and 38% with teleost (modern bony fish) PRLs. Moreover, the PRL contains three disulfide bonds homologous to those of tetrapod PRLs and differs from teleost PRLs which lack the amino-terminal disulfide bond. Thus, the structural features of lungfish PRL indicate a closer relationship to tetrapod PRLs than to teleost PRLs. All PRLs sequenced to date share 22 common amino acids, which may be important for the activities common to all PRLs.

Purification of growth hormones by reversed-phase high-performance liquid chromatography

Reversed-phase high-performance liquid chromatography (HPLC) on a column of Radial-Pak C18 cartridge was utilized for the purification of a variety of growth hormone (GH) proteins from mammalian, avian, amphibian and fish pituitary glands. Recovery of GH from pituitary glands of up to 0.43% of total protein was obtained with a high degree of homogeneity as revealed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The HPLC-purified GHs show reactions of identity or near identity by immuno-diffusion studies on agar gel. This method offers a convenient and rapid purification of vertebrate GH on an analytical or preparative scale.

Pituitary as a target organ for toxic effects of P4501A1 inducing chemicals

We report here that cytochrome P4501A1 in the male rainbow trout pituitary is highly inducible by beta-naphthoflavone. Pituitary cells containing inducible P4501A1 were identified by double immunostaining as gonadotrophs containing gonadotropin II. Thus, the pituitary gonadotrophs may be target cells for polyaromatic hydrocarbons. Elevated plasma levels of gonadotropin II (GTH II) and testosterone in the induced fish indicated that the functioning of the pituitary was disturbed. Because GTH II regulate the final stage of sexual maturation the results implies that exposure to P4501A1 inducing compounds may disturb this development stage.

Identification of growth hormone molecular variants in chicken serum

It has been described that pituitary growth hormone shows molecular and functional heterogeneity. In birds, size and charge variants of chicken growth hormone (cGH) have been shown in the chicken pituitary gland and in purified preparations of the hormone. Here we demonstrate the existence of cGH molecular isoforms in chicken serum, thus suggesting that they are secreted from the gland. The isolation of total cGH present in sera was performed by immunoaffinity chromatography employing a specific monoclonal antibody against cGH. Different analytical electrophoretic methods (SDS-polyacrylamide gel electrophoresis, isoelectric focusing, bidimensional polyacrylamide gel electrophoresis) followed by Western blot and immunostaining were employed to characterize the serum cGH isoforms, and compared to those present in a fresh pituitary extract. Several identical immunoreactive bands comigrated in both serum and the gland extract in the different systems (SDS-PAGE, MW 16, 22, 26, 29, 52, 62, 66 kDa; IEF, pIs 8.1, 7.5, 7.1, 6.8, 6.2), thus revealing a high correspondence of molecular isoforms of the hormone in the two tissues. Additionally, a glycosylated variant of chicken growth hormone (G-cGH) was also revealed in the serum after concanavalin A-Sepharose chromatography.

Developmental expression of the growth hormone gene in the gilthead sea bream Sparus aurata

Expression of growth hormone (GH) gene during early stages of larval development of the teleost Sparus aurata was determined by Northern blot analysis. Poly(A+) RNA was prepared from a pool of larvae collected on different days after hatching. When hybridized to Sparus aurata GH cDNA, GH specific mRNA was first seen on day 6 post-hatching. In contrast, the levels of beta-actin mRNA, which was used to normalize for RNA amounts, were already high on the day of hatching. Our results suggest that expression of the GH gene is very low immediately after hatching, and increases dramatically within 6 days.

Stimulation of hepatic thyroxine 5'-deiodinase activity in rainbow trout (Oncorhynchus mykiss) by Pacific salmon growth hormone

1. Growth hormone extracted from Pacific salmon pituitaries (sGH) was injected intra-peritoneally into rainbow trout to determine sGH effects on plasma levels of thyroxine (T4), 3,5,3'-triiodothyronine (T3) and properties of the hepatic 5'-deiodinase enzyme (5'-D) responsible for T4 to T3 conversion. 2. After 24 hr, sGH (0.1 or 0.5 microgram/g) did not alter the plasma T4 level or 5'-D, Km, but elevated plasma T3 and especially 5'-D Vmax. 3. Thus sGH, like the previously tested human GH, acutely enhances the potential for extra-thyroidal T3 production in trout by increasing the functional level of hepatic 5'-D, but without changing the plasma T4 level.