Biomedical subjects

Yoshio Takei

Publications and source records attributed to Yoshio Takei.

At least 37 records · Page 2Linked to original sources

PubMed2004

cDNA cloning and functional expression of a Ca2+-sensing receptor with truncated C-terminal tail from the Mozambique tilapia (Oreochromis mossambicus).

The complete cDNA sequence of the tilapia extracellular Ca(2+)-sensing receptor (CaR) was determined. The transcript length of tilapia CaR (tCaR) is 3.4 kbp and encodes a 940-amino acid, 7-transmembrane domain protein that is consistent in its structural features with known mammalian and piscine CaRs. The tCaR extracellular domain includes a characteristic hydrophobic segment, conserved cysteine residues that are implicated in receptor dimerization (Cys(129) and Cys(131)) and in coupling to the transmembrane domain (nine conserved cysteine residues), and conserved serine residues (Ser(147) and Ser(169-171)) that are linked to receptor binding of Ca(2+) and L-amino acid-mediated potentiation of function. mRNA expression of tCaR was strong in kidney, brain, and gill. Weaker expression was observed in pituitary, stomach, intestine, urinary bladder, and heart. This distribution is consistent with possible physiological roles in endocrine cells, excitable tissues, and ion-transporting barrier epithelia. Expression of tCaR mRNA in kidney and intestine was salinity-dependent, suggesting a role for the receptor in iono-/osmoregulation in this euryhaline teleost species. Human embryonic kidney-293 cells transiently transfected with tCaR cDNA demonstrated dose-dependent phospholipase C activation in response to elevations in the extracellular Ca(2+) concentration ([Ca(2+)](o)). Functional activation of the mitogen-activated protein kinase cascade by high [Ca(2+)](o) was also confirmed in these cells despite the naturally occurring truncation of the receptor's intracellular tail, which removes segments variably linked in mammalian CaRs to filamin-coupled activation of mitogen-activated protein kinase cascades. Sensitivity of phospholipase C activation to [Ca(2+)](o) was dependent on the ionic strength of the bathing medium, supporting a role in salinity sensing.

Amino Acid Sequence↗

PubMed2004

Neurohypophysial hormones of dogfish, Triakis scyllium: structures and salinity-dependent secretion.

Sharks and rays utilize a unique strategy for adaptation to the hyperosmotic marine environment by maintaining their plasma slightly hyperosmotic to surrounding seawater (SW) through the accumulation of urea. Since neurohypophysial hormones (NHs) are plausible candidates for osmoregulatory effectors, the synthesis and release of NHs were investigated after transfer of fish to different environmental salinities. Molecular cloning revealed three NHs from the hypothalamus of a dogfish, Triakis scyllium: vasotocin (VT), asvatocin, and a novel oxytocin-family peptide, phasitocin ([Phe3, Asn4, Ile8]vasotocin). The VT precursor consists of a signal peptide, VT, a neurophysin and a copeptin moiety. In contrast, the asvatocin and phasitocin precursors are shorter due to the lack of a copeptin moiety as is the case in oxytocin and mesotocin precursors in tetrapods and lungfish, but different from teleost isotocin precursors that have the copeptin moiety. In the hypothalamus, VT mRNA levels significantly increased after transfer to concentrated (130%) SW for 2 days, while no change was observed in mRNA levels of asvatocin and phasitocin following transfer to either 130% or diluted (60%) SW. The increase in VT mRNA was reflected in the plasma level of peptide; plasma VT concentration measured by highly sensitive and specific radioimmunoassay increased according to elevated environmental salinities. These results suggest that VT is an osmoregulatory effector in dogfish, especially when the dogfish is exposed to a hyperosmotic environment.

Amino Acid Sequence↗

PubMed2004

Renal effects of a new member of adrenomedullin family, adrenomedullin2, in rats.

A new member of the adrenomedullin family, adrenomedullin2, was identified in mammals. The effects of adrenomedullin2 on renal hemodynamics and urine formation were examined in rats. Intrarenal arterial infusion of adrenomedullin2 at rates of 30, 100 and 300 pmol/kg/min decreased blood pressure and increased heart rate in a dose-dependent fashion. Adrenomedullin2 infusion at 100 pmol/kg/min significantly increased renal blood flow and urine flow. At the higher infusion rate (300 pmol/kg/min), adrenomedullin2 significantly decreased urine flow. Continuous intrarenal infusion of adrenomedullin2 at 100 pmol/kg/min significantly increased renal blood flow from 6.7+/-0.5 to 8.8+/-0.5 ml/min and decreased renal vascular resistance from 16+/-1 to 11+/-1 mm Hg min/ml. Urine flow was significantly increased from 21.5+/-4.9 to 36.2+/-8.5 microl/min and urinary excretion of sodium was increased from 2.3+/-0.9 to 4.9+/-1.4 microEq/min. Blood pressure, heart rate and glomerular filtration rate did not change. Infusion of a similar dose of adrenomedullin also increased renal blood flow (6.8+/-0.4-8.8+/-0.6 ml/min), urine flow (25.4+/-3.2-42.8+/-9.4 microl/min) and urinary excretion of sodium (2.8+/-0.6-6.5+/-1.2 microEq/min), decreased renal vascular resistance (15+/-1-11+/-1 mm Hg min/ml) and did not alter glomerular filtration rate. Thus, the renal actions induced by adrenomedullin2 were similar to those of adrenomedullin. These data suggest that adrenomedullin2 may play an important role in the regulation of renal hemodynamics and urine formation.

Adrenomedullin↗

PubMed2004

FHL5, a novel actin-binding protein, is highly expressed in eel gill pillar cells and responds to wall tension.

Supporting evidence for the contractile nature of fish branchial pillar cells was provided by demonstrating the presence of actin fibers and a novel four-and-a-half LIM (FHL) protein in which expression is specific for contractile tissues and sensitive to the tension applied to the pillar cell. When eel gill sections were stained with rhodamine-phalloidin, a selective fluorescent probe for fibrous actin, a strong bundle-like staining was observed around collagen columns in pillar cells, suggesting the presence of abundant actin fibers. A cDNA clone encoding a novel member of the actin-binding FHL family, FHL5, was isolated from a subtracted cDNA library of eel gill. Northern analysis revealed that FHL5 mRNA is highly expressed only in gills, heart, and skeletal muscle. In gills, FHL5 was found to be confined to pillar cells by immunohistochemistry. Confocal fluorescence microscopy showed that FHL5 is present in both cytosol and nucleus; within the cytosol, a large portion of FHL5 is colocalized with the phalloidin-positive actin bundles. Furthermore, transfection of myogenic C2C12 cells with FHL5 cDNA demonstrated, in addition to its interaction with actin stress fibers, a nuclear shuttling activity of FHL5. The mRNA and protein levels were found to be elevated on 1) transfer of eels from seawater to freshwater, 2) volume expansion by infusion of isotonic dextran-saline, and 3) constriction of gill vasculature by bolus injection of endothelin-1. These results suggest contractile nature of pillar cells and a role of FHL5 in maintaining the integrity and regulating the dynamics of pillar cells.

Actins↗

PubMed2004

Identification of novel adrenomedullin in mammals: a potent cardiovascular and renal regulator.

We have identified cDNA encoding a new member of the adrenomedullin (AM) family, AM2, for the first time in mammals (mouse, rat and human). The predicted precursor carried mature AM2 in the C-terminus, which had an intramolecular ring formed by an S-S bond and a possibly amidated C-terminus. Phylogenetic analyses clustered AM2 and AM into two distinct but closely related groups. Similarity of exon-intron structure and synteny of neighboring genes showed that mammalian AM2 is an ortholog of pufferfish AM2 and a paralog of mammalian AM. AM2 mRNA was expressed in submaxillary gland, kidney, stomach, ovary, lymphoid tissues and pancreas of mice, but not in adrenal and testis. Intravenous injection of synthetic mature AM2 decreased arterial pressure more potently than AM, and induced antidiuresis and antinatriuresis in mice. These results show that at least two peptides, AM and AM2, comprise an adrenomedullin family in mammals, and that AM2 may play pivotal roles in cardiovascular and body fluid regulation.

Adrenomedullin↗

PubMed2004

Novel fish-derived adrenomedullin in mammals: structure and possible function.

Adrenomedullin (AM) has been recognized as a member of the calcitonin (CT)/CT gene-related peptide (CGRP) family. However, an independent AM family consisting of five paralogous peptides exists in teleost fish. Among them, the peptide named AM1 is an ortholog of mammalian AM as determined by the linkage analysis of orthologous genes and the presence of proAM N-terminal 20 peptide (PAMP)-like sequence in the prosegment. Since the peptides named AM2 and 3 are distinct from other members with respect to the precursor sequence, tissue distribution of the transcripts, and exon-intron organization, we searched for their mammalian orthologs from genome databases, which resulted in an identification of AM2 in human, rat, and mouse. AM2 was expressed abundantly in the submaxillary gland, kidney, and some vascular and digestive tissues of mice. AM2 injected in vivo induced potent cardiovascular and renal effects in mice. In the heart and kidney of mice, AM2 was localized in endothelial cells of the coronary vessels and in glomeruli and vasa recta, respectively. AM2 increased cAMP accumulation in cells expressing human CT receptor-like receptor (CRLR) and one of receptor activity-modifying proteins (RAMPs), but it was no more potent than CGRP and AM. AM2 was also less potent than CT in cells expressing CT receptor and RAMP. There remains a possibility that a new AM2-specific receptor or an additional RAMP that enables CRLR to be an AM2-specific receptor, exists in mammals.

Adrenomedullin↗

PubMed2004

Identification of angiotensin I in several vertebrate species: its structural and functional evolution.

In order to delineate further the molecular evolution of the renin-angiotensin system in vertebrates, angiotensin I (ANG I) has been isolated after incubation of plasma and kidney extracts of emu (Dromiceus novaehollandiae), axolotl (Ambystoma mexicanum), and sea lamprey (Petromyzon marinus). The identified sequences were [Asp1, Val5, Asn9] ANG I in emu, [Asp1, Val5, His9] ANG I in axolotl, and [Asn1, Val5, Thr9] ANG I in sea lamprey. These results confirmed the previous findings that tetrapods have Asp and fishes including cyclostomes have Asn at the N-terminus, and that the amino acid residue at position 9 of ANG I was highly variable but, those at other positions were well conserved among different species. Since Asp and Asn are convertible during incubation, angiotensinogen sequences were searched in the genome and/or EST database to determine the N-terminal amino acid residue from the gene. The screening detected 12 tetrapod (10 mammalian, one avian, and one amphibian) and seven teleostean angiotensinogen sequences. Among them, all tetrapods have [Asp1] ANG except for Xenopus, and all teleosts have [Asn1] ANG, thereby confirming the above rule. Comparison of the vasopressor activity in the eel revealed that [Asn1] ANG I and II were more potent than [Asp1] peptides, which was opposite to the previous results in mammals and birds, in which [Asp1] ANG I and II were more potent. Collectively, the present results support the general rule that tetrapods have [Asp1] ANG and fishes including cyclostomes have [Asn1] ANG. However, an aquatic anuran (Xenopus) has [Asn1] ANG in its gene despite another aquatic urodele (axolotl) has [Asp1] ANG. From the functional viewpoint, homologous [Asn1] ANG was more potent in fish as is homologous [Asp1] ANG in tetrapods, suggesting that ANG II molecule has undergone co-evolution with its receptor during vertebrate phylogeny.

Ambystoma↗

PubMed2004

Coronary vasodilatory response to a novel peptide, adrenomedullin 2.

1. Adrenomedullin-2 (AM2) is a novel peptide originally found in a fish and it is structurally related to mammalian AM or fish AM1. Cloning of AM2 cDNA in the mouse, rat and human has been successful. In the present study, the vasodilatory effect of synthetic human AM2 was analysed in isolated artery ring preparations of porcine. 2. Vasodilatory effect of AM2 was the most potent in the coronary artery, followed by the carotid and supramesenteric arteries, but absent in the femoral, pulmonary and renal arteries. 3. The effect of AM2 was equipotent with that of human AM/AM1 in these arteries. 4. AM2-induced relaxation was inhibited by human CGRP (8-37), but not by human AM/AM1 (22-52), suggesting that the vasodilatory response to AM2 is mediated through the CGRP1 receptor. 5. AM2 may share the same receptor (complex) with AM/AM1 for the vasorelaxation. This is the first report of the vasodilatory responses to AM2 in isolated vasculature.

Animals↗

PubMed2004

A facilitative urea transporter is localized in the renal collecting tubule of the dogfish Triakis scyllia.

Reabsorption of filtered urea by the kidney tubule is essential for retaining high levels of urea in body fluids of marine elasmobranchs. To elucidate the mechanisms of urea reabsorption, we examined the distribution of a facilitative urea transporter (UT) in the kidney of the dogfish Triakis scyllia. We isolated a cDNA encoding a UT that is homologous to the facilitative UT cloned from another dogfish species, Squalus acanthias. The Triakis UT mRNA is abundantly expressed in the kidney, while low levels of expression were detected in the brain and liver. In the dogfish kidney, each nephron makes four turns and traverses repeatedly between bundle zone and sinus zone. In the bundle zone, the resulting five tubular segments are arranged in a countercurrent loop fashion. Immunohistochemistry using specific antibodies raised against the cloned UT revealed that, among the nephron segments, the UT is expressed exclusively in the final segment of the bundle zone, i.e. in the collecting tubule of the Triakis kidney. In contrast to the limited localization of UT, the transport enzyme Na+/K+-ATPase is distributed in the basolateral membrane of numerous tubular segments both in the sinus zone and the bundle zone. However, in the collecting tubule, Na+/K+-ATPase immunoreactivity was not detected. The present study suggests that the collecting tubule is responsible for the reabsorption of urea in the marine elasmobranch kidney. Other countercurrent segments may contribute to production of a driving force for facilitative diffusion of urea through the UT.

Amino Acid Sequence↗

PubMed2004

Identification of angiotensin I in a cyclostome, Lampetra fluviatilis.

Angiotensin I (ANG I) was isolated from incubates of plasma and kidney extracts of the river lamprey, Lampetra fluviatilis, using eel vasopressor activity as an assay during purification. Its sequence was Asn-Arg-Val-Tyr-Val-His-Pro-Phe-Thr-Leu as determined by the sequence analysis and mass spectrometry. The sequence was confirmed by identity of the elution profile with the synthetic peptide in two different reverse-phase columns of high-performance liquid chromatography. Lamprey ANG I produced dorsal-aortic pressor responses in L. fluviatilis but the rise was very small in comparison to that produced by angiotensin II. Angiotensin III produced an even bigger increase. It was not possible to demonstrate a difference in response to Asn(1) (lamprey) ANG I and Asp(1) (human) ANG I. The present study directly demonstrated the presence and biological activity of the renin-angiotensin system in the most primitive extant vertebrates, the cyclostomes. Thus the renin-angiotensin system is a phylogenetically old hormonal system that is present throughout the vertebrates.

Analysis of Variance↗

PubMed2003

Identification of a novel adrenomedullin gene family in teleost fish.

Adrenomedullin (AM) is a multifunctional peptide known to form a hormone family with calcitonin gene-related peptide (CGRP) and amylin. We have cloned five distinct AM cDNAs from the pufferfish, Takifugu rubripes, and named them TrAM-1, -2, -3, -4, and -5. Judging from the deduced precursor sequences and processing pattern of the C-terminal mature peptides, TrAMs may be divided into at least two groups; AM-2 and -3, and AM-1, -4, and possibly -5. Phylogenetic analysis of the mature peptides, exon-intron structure of their genes, and tissue distribution of their mRNA also support this classification. TrAM-1 and -4 were ubiquitously expressed in various tissues including the kidney and interrenal (adrenal homolog) as in the case of mammalian AM, while TrAM-2 and -3 were expressed most abundantly in the brain followed by the vascular tissues. Synteny of the genes around AM gene showed that TrAM-1 is the ortholog of mammalian AM. The presence of a PAMP-like sequence in the prosegment of TrAM-1 also supports this notion. Multiple AMs were also detected in another pufferfish, Tetraodon nigroviridis, and in zebrafish, Danio rerio. The present study shows for the first time the presence of a novel AM family in teleost fish that is independent from CGRP and amylin, which further suggests the possible existence of multiple AMs in mammals.

Adrenomedullin↗

PubMed2003

Four functionally distinct C-type natriuretic peptides found in fish reveal evolutionary history of the natriuretic peptide system.

Natriuretic peptides (NPs) are major cardiovascular and osmoregulatory hormones in vertebrates. Although tetrapods generally have three subtypes, atrial NP (ANP), B-type NP (BNP), and C-type NP (CNP), some teleosts lack BNP, and sharks and hagfish have only one NP. Thus, NPs have diverged during fish evolution, possibly reflecting changes in osmoregulatory systems. In this study, we found, by cDNA cloning, four distinct CNPs (1 through 4) in the medaka (Oryzias latipes) and puffer fish (Takifugu rubripes), although to our knowledge no more than two CNPs have been isolated from a vertebrate species. Predicted mature CNP-1 was most similar, and CNP-4 was most dissimilar, to mammalian CNPs. However, synthetic CNP-4 most potently activated OlGC1, a medaka CNP-specific receptor (NPR-B) expressed in cultured cells, whereas CNP-1 and CNP-3 most activated OlGC7 and OlGC2, two medaka homologues of the ANP/BNP receptor (NPR-A), respectively. Linkage mapping in medaka followed by comparative genomic analyses among fishes and humans located four CNP genes in separate medaka chromosomes corresponding to human chromosomes 1, 2, 12, and 17. From conserved synteny, the following evolutionary history of NPs was evoked: (i) four CNP genes were generated by chromosomal duplications before the divergence of elasmobranchs; (ii) the CNP-3 gene generated ANP and BNP genes through tandem duplication before the divergence of tetrapods and teleosts; (iii) CNP-1 and -2 genes were retained in the teleost lineage but not in the tetrapod lineage; (iv) the CNP-3 gene disappeared from the tetrapod lineage after divergence of amphibians; and (v) the CNP-4 gene is retained in humans as CNP.

Amino Acid Sequence↗

PubMed2003

A novel guanylin family (guanylin, uroguanylin, and renoguanylin) in eels: possible osmoregulatory hormones in intestine and kidney.

As the intestine is an essential organ for fish osmoregulation, the intestinal hormone guanylins may perform major functions, especially in euryhaline fish such as eels and salmonids. From the intestine of an eel, we identified cDNAs encoding three distinct guanylin-like peptides. Based on the sequence of mature peptide and sites of production, we named them guanylin, uroguanylin, and renoguanylin. Renoguanylin is a novel peptide that possesses the characteristics of both guanylin and uroguanylin and was abundantly expressed in the kidney. By immunohistochemistry, guanylin was localized exclusively in goblet cells, but not enterochromaffin cells, of the intestine. After transfer of eels from fresh water to seawater, mRNA expression of guanylin and uroguanylin did not change for 3 h, but it increased after 24 h. The increase was profound (2-6-fold) after adaptation to seawater. The expression of uroguanylin was also up-regulated in the kidney of seawater-adapted eels, but that of renoguanylin was not so prominent as other guanylins in both intestine and kidney. Collectively, the novel eel guanylin family appears to have important functions for seawater adaptation, particularly long-term adaptation. Eel guanylin may be secreted from goblet cells into the lumen with mucus in response to increased luminal osmolality and act on the epithelium to regulate water and salt absorption.

Amino Acid Sequence↗

PubMed2003

Effects of angiotensin II and natriuretic peptides of the eel on prolactin and growth hormone release in the tilapia, Oreochromis mossambicus.

The effects of angiotensin II (ANG II) and natriuretic peptides (NPs) of the eel (ANP, atrial natriuretic peptide; CNP, C-type natriuretic peptide; and VNP, ventricular natriuretic peptide) on prolactin (PRL(188) and PRL(177)) and growth hormone (GH) release from the organ-cultured tilapia pituitary were examined. Eel ANG II at concentrations greater than 1 nM stimulated the release of PRL(188) and PRL(177) in a dose-related manner during the first hour of incubation. Significant stimulation by 100 nM ANG II on PRL(177) release was observed until 4h of incubation, and on PRL(188) release until 12 h. No effect of ANG II was seen on GH release. None of the NPs altered the release of PRLs at any time point. On the other hand, eel VNP at concentrations greater than 1 nM stimulated GH release in a dose-related manner after 4 h, and significant stimulation was observed until 48 h. Eel CNP was less effective than eel VNP; significant stimulation of GH release was observed at 1 and 10 nM during 24-48 h of incubation. No significant effect of eel ANP on GH release was seen at any concentration. ANG II had no effect on GH release at any time point. There was no change in mRNA levels of PRLs or GH in the pituitaries incubated with ANG II for 8 h or those incubated with the NPs for 48 h. These results indicate rapid and short-lasting stimulation by ANG II on PRL release and slow and long-lasting stimulation by VNP and CNP on GH release from the tilapia pituitary.

Analysis of Variance↗

PubMed2003

Ambient salinity-dependent effects of homologous natriuretic peptides (ANP, VNP, and CNP) on plasma cortisol level in the eel.

The effects of three eel natriuretic peptides (NPs), i.e., ANP, VNP, and CNP on plasma cortisol levels were investigated in conscious freshwater (FW)- and seawater (SW)-adapted eels with permanent arterial catheter. The experiment was performed between 9:00 and 15:00 of the day, when the natural plasma cortisol level was relatively stable. After a single intra-arterial injection of ANP, VNP, or CNP at 100 pmol/kg, only CNP, but not ANP or VNP, increased plasma cortisol concentration in FW eels. In SW eels, however, only ANP at the same dose increased plasma cortisol concentration. The effect of CNP in FW eels and that of ANP in SW eels were dose-dependent between 10 and 1000 pmol/kg. On the other hand, ANP and VNP were equally effective, but CNP was ineffective, in increasing hematocrit in both FW and SW eels. These results show that the effect of NPs on plasma cortisol level is dependent on the ambient salinity in the eel. Since cortisol plays a pivotal role in environmental adaptation of fishes, the results suggest a possible involvement of ANP and CNP in the adaptation to SW and FW, respectively. Furthermore, this is the first evidence showing that ANP and VNP exert different effects in fish despite they share the same receptor, NPR-A.

Adaptation, Physiological↗

PubMed2003

C-type natriuretic peptide of rainbow trout (Oncorhynchus mykiss): primary structure and vasorelaxant activities.

Natriuretic peptides (NPs) play important roles in osmoregulatory and cardiovascular systems of vertebrates. For functional studies of NPs, rainbow trout (Oncorhynchus mykiss), a euryhaline fish, is an interesting model. The information on homologous NPs of salmonid fish is, however, still incomplete with respect to C-type NP (CNP). In this study, we isolated cDNAs encoding the precursor of CNP from the brain of trout. Predicted mature CNP (CNP-22) sequence was identical to that of killifish Fundulus heteroclitus, and only one amino acid was different from that of the eel Anguilla japonica, demonstrating a greater conservation among different teleost species than is found with atrial NP (ANP) and ventricular NP (VNP). While the preprosegment of trout CNP retained 57% similarity to the eel sequence, similarities were low to those of sharks and tetrapods. The major site of expression identified by RT-PCR was the brain with minor expression in the atrium. The putative mature CNP-22 was synthesized and its biological activity was compared with other trout NPs (ANP and VNP) using trout ventral aorta, efferent branchial and celiacomesenteric arteries and anterior cardinal vein in vitro. Synthetic trout CNP-22 relaxed all pre-contracted vessels with potencies comparable to trout ANP and VNP.

Amino Acid Sequence↗

PubMed2003

Isolation, synthesis, and biological activity of flounder [Asn1,Ile5,Thr9] angiotensin I.

A novel angiotensin I (ANG I) has been isolated from incubates of plasma and kidney extracts of the flounder, Platichthys flesus, using ion-exchange, gel-permeation, and reverse-phase high performance liquid chromatography (HPLC). Its sequence was determined as H-Asn-Arg-Val-Tyr-Ile-His-Pro-Phe-Thr-Leu-OH by sequence analysis and mass spectrometry. No vasopressor activity was detected at the elution position of [Asp(1)] ANG I in ion-exchange HPLC. The sequence was confirmed by identity of the elution position with the synthetic peptide in two different HPLC systems. When compared with ANG I isolated from other teleost fish, flounder ANG I uniquely has an isoleucine at position 5 rather than valine. Injection of angiotensin II (ANG II) into chronically cannulated flounder resulted in a dose-dependent pressor response, native [Asn(1),Ile(5)] ANG II, was found to elicit pressor responses comparable with those seen when teleost [Asn(1),Val(5)] ANG II and human [Asp(1),Ile(5)] ANG II were injected into flounder over the dose range 0.02-1.00 nmol/kg(-1). Plasma concentrations of the neurohypophysial peptide AVT were measured in chronically cannulated flounder following the injection of ANG II to examine the effect of ANG II on circulating AVT concentration. The injection of [Asn(1),Ile(5)] ANG II (1 nmolkg(-1)) or [Asp(1),Ile(5)] ANG II (2.5 nmolkg(-1)) resulted in a significant fall in the circulating levels of AVT suggesting that ANG II either directly or indirectly negatively influences AVT secretion.

Amino Acid Sequence↗

PubMed2003

Growth hormone and insulin-like growth factor I of a Euryhaline fish Cottus kazika: cDNA cloning and expression after seawater acclimation.

The four-spine sculpin Cottus kazika is a euryhaline teleost, in which faster growth in seawater (SW) and freshwater (FW) has been reported. In this study, cDNA clones encoding growth hormone (GH) and insulin-like growth factor I (IGF-I) were isolated from this species to examine the involvement of the GH/IGF-I axis in osmotic adaptation. The amino acid sequence of GH predicted from cDNA was highly similar to those of other fish species, 92% to Sparus aurata, 67% to Paralichthys olivaceus, and 63% to Oncorhynchus keta. The predicted sequence of IGF-I was also exhibited high similarity to those of other fishes, 97% to Myxocephalus scorpius, 95% to P. olivaceus, and 81% to O. keta. Tissue distribution of GH and IGF-I mRNA in fish reared in FW and SW was examined by reverse transcription-polymerase chain reaction (RT-PCR). The GH mRNA was detected only in the pituitary gland. The major site of IGF-I mRNA expression was the liver while minor signals were detected in various tissues including the pituitary, gill, fin, heart, spleen, intestine, and kidney. The expression level of GH mRNA in the pituitary was not different between FW- and SW-reared fish. However, the level of IGF-I mRNA in the liver of SW-reared fish was significantly higher than that of FW-reared fish. These results suggest the possible involvement of hepatic IGF-I in SW adaptation of this species.

Adaptation, Physiological↗