Molecular characterisation and expression of parathyroid hormone-related protein in the caudal neurosecretory system of the euryhaline flounder, Platichthys flesus.

Parathyroid hormone-related protein (PTHrP) is a hypercalcemic factor in fish, but the source of circulating PTHrP remains unclear. In this study investigation of the caudal neurosecretory system (CNSS), considered one of major sources of PTHrP in fish, provided valuable insights into this regulatory system. We report pthrpa and pthrpb gene cloning, characterization, expression, and responses to low salinity and hypocalcemia challenge in flounder.

Molecular Characterization and Expression of α-Globin and β-Globin Genes in the Euryhaline Flounder (Platichthys flesus).

In order to understand the possible role of globin genes in fish salinity adaptation, we report the molecular characterization and expression of all four subunits of haemoglobin, and their response to salinity challenge in flounder. The entire open reading frames of α1-globin and α2-globin genes were 432 and 435 bp long, respectively, whereas the β1-globin and β2-globin genes were both 447 bp. Although the head kidney (pronephros) is the predicted major site of haematopoiesis, real-time PCR revealed that expression of α-globin and β-globin in kidney (mesonephros) was 1.

Potent cardiovascular effects of homologous urotensin II (UII)-related peptide and UII in unanesthetized eels after peripheral and central injections.

We cloned cDNAs encoding urotensin II (UII)-related peptide (URP) and UII in Japanese eel, Anguilla japonica, the former being the first such cloning in teleost fishes. Unlike the exclusive expression of UII in the urophysis, the URP gene was expressed most abundantly in the brain (medulla oblongata) followed by the urophysis. Peripheral injections of URP into eels increased blood pressure by 16.

The corpuscles of Stannius, calcium-sensing receptor, and stanniocalcin: responses to calcimimetics and physiological challenges.

This study has examined whether the calcium-sensing receptor (CaSR) plays a role in control of stanniocalcin-1 (STC-1), the dominant calcium regulatory hormone of fish, comparable with that demonstrated for CaSR in the mediation of ionized calcium regulation of PTH secretion in mammals. In a previous study, we have cloned flounder STC-1 from the corpuscles of Stannius (CS). Here, we report the cloning and characterization of the CS CaSR, and the in vivo responses of this system to altered salinity, EGTA induced hypocalcemia, and calcimimetic administration.

Enhanced renal sensitivity of the spontaneously hypertensive rat to urotensin II.

Urotensin II (UII) has been implicated widely in cardiovascular disease. The mechanism(s) through which it contributes to elevated blood pressure is unknown, but its emerging role as a regulator of mammalian renal function suggests that the kidney might be involved. The aim of this study was to determine the effect of UII on renal function in the spontaneously hypertensive rat (SHR).

Cortisol and prolactin modulation of caudal neurosecretory system activity in the euryhaline flounder Platichthys flesus.

Previous studies have shown roles for cortisol and prolactin in osmoregulatory adaptation to seawater and freshwater, respectively, in euryhaline fish. This study of the European flounder investigated the potential for these hormones to modulate activity of the caudal neurosecretory system (CNSS), which is thought to be involved in physiological adaptation to changing external salinity. Superfusion of isolated CNSS with either cortisol or prolactin (10 microM; 15 min) led to changes in firing activity in neuroendocrine Dahlgren cells, recorded extracellularly.

Renal haemodynamic and tubular actions of urotensin II in the rat.

Urotensin II (UTS) is a potent vasoactive peptide that was originally identified in teleost fish. Mammalian orthologues of UTS and its receptor (UTSR) have been described in several species, including humans and rats. We have shown previously that bolus injections of UTS caused a decrease in urine flow and sodium excretion rates in parallel with marked reductions in renal blood flow (RBF) and glomerular filtration rate (GFR).

Seasonal changes in peptide, receptor and ion channel mRNA expression in the caudal neurosecretory system of the European flounder (Platichthys flesus).

The caudal neurosecretory system (CNSS) of the euryhaline flounder Platichthys flesus has suggested roles in osmoregulatory, reproductive and nutritional adaptation, as fish migrate between seawater (winter) and brackish/freshwater (summer) environments. This study examined seasonal changes in mRNA expression profile of functionally important genes in the CNSS. cDNAs encoding neuropeptides, receptors and ion channels were cloned by reverse transcriptase polymerase chain reaction (RT-PCR) and screening of a flounder CNSS cDNA library.

Evidence for nitric oxide role in the caudal neurosecretory system of the European flounder, Platichthys flesus.

A neuromodulatory role for nitric oxide has been reported for magnocellular neuroendocrine cells in mammalian hypothalamus. We examined its potential as a local intercellular messenger in the neuroendocrine Dahlgren cell population of the caudal neurosecretory system (CNSS) of the euryhaline flounder. Immunocytochemistry using an antibody raised against human neuronal nitric oxide synthase (NOS) indicated the presence of NOS in the Dahlgren cells.

Fish caudal neurosecretory system: a model for the study of neuroendocrine secretion.

The caudal neurosecretory system (CNSS) is unique to fish and has suggested homeostatic roles in osmoregulation and reproduction. Magnocellular neuroendocrine Dahlgren cells, located in the terminal segments of the spinal cord, project to a neurohaemal organ, the urophysis, from which neuropeptides are released. In the euryhaline flounder Platichthys flesus Dahlgren cells synthesise at least four peptides, including urotensins I and II and CRF.

Molecular characterization and expression of urotensin II and its receptor in the flounder (Platichthys flesus): a hormone system supporting body fluid homeostasis in euryhaline fish.

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.

Day-night specific binding of 2-[125I]iodomelatonin and melatonin content in gill, small intestine and kidney of three fish species.

Some of melatonin's (Mel) well-established physiological effects are mediated via high-affinity cell-membrane receptors belonging to the superfamily of G-protein-coupled receptors. Specific binding of ligand 2-[(125)I]iodomelatonin, using membrane preparations from osmoregulatory tissues of flounder, rainbow trout and sea bream, together with Mel concentrations in the tissues and plasma were studied. The kidney, gill and small intestine samples were collected during the day and at night.

Stanniocalcin in the euryhaline flounder (Platichthys flesus): primary structure, tissue distribution, and response to altered salinity.

Stanniocalcin (STC) is a homodimeric glycoprotein hormone that was first discovered in fish, where it is largely produced by a unique endocrine gland, the corpuscles of Stannius (CS). In bony fish, it is thought to be an important regulator of calcium and phosphate uptake from the aquatic environment. This report describes the molecular cloning of STC from euryhaline flounder (Platichthys flesus) CS cDNA and genomic DNA.

Increased renal tubular reabsorption of calcium and magnesium by the offspring of diabetic rat pregnancy.

Diabetic pregnancy has a marked influence on offspring calcium and magnesium homeostasis. Urinary excretion of calcium and magnesium is reduced, yet offspring of diabetic pregnancy exhibit hypomagnesemia and hypocalcemia. The aim of this study was to measure renal hemodynamic and tubular function in the offspring of diabetic (OD) and control, nondiabetic (OC) rats at 4 and 8 wk of age to determine the glomerular and tubular mechanisms through which renal calcium and magnesium handling are programmed in utero.

Rapid natriuretic action of aldosterone in the rat.

Rapid, nongenomic actions of aldosterone have been demonstrated in a number of cell types in vitro, including renal cell lines, but there remains little direct evidence that it is able to exert rapid effects on the kidney in the whole animal. Accordingly, the aim of this study was to determine whether aldosterone induces rapid changes in the renal handling of electrolytes or acid-base balance in the anesthetized rat. With the use of a servo-controlled fluid replacement system, spontaneous urine output by anesthetized male Sprague-Dawley rats was replaced with 2.

Biochemical characterization and immunohistochemical localization of urotensin II in the human brainstem and spinal cord.

The human urotensin II (UII) precursor encompasses several potential cleavage sites and thus, processing of pro-UII may generate various forms of mature UII including the peptides of 11 (UII11), 16 (UII16) and 19 (UII19) residues. Until now, the native form of human UII had not been characterized. Here, we show that the major UII peptide occurring in the human spinal cord corresponds to UII11.

Coexpression of corticotropin-releasing hormone and urotensin i precursor genes in the caudal neurosecretory system of the euryhaline flounder (Platichthys flesus): a possible shared role in peripheral regulation.

CRH and urotensin I (UI) are neuroendocrine peptides that belong to the superfamily of corticotropin-releasing factors. In mammals, these peptides regulate the stress response and other central nervous system functions, whereas in fish an involvement for UI in osmoregulation has also been suggested. We have identified, characterized, and localized the genes encoding these peptides in a unique fish neuroendocrine organ, the caudal neurosecretory system (CNSS).

Renal action of acute chloroquine and paracetamol administration in the anesthetized, fluid-balanced rat.

Chloroquine induces diuresis, natriuresis, and an increase in glomerular filtration rate (GFR) in the rat. These responses are modified in rats with analgesic nephropathy induced by long-term paracetamol (acetaminophen) administration. Here, the effects of acute paracetamol treatment on renal function and the response to chloroquine are reported.

Renal function in a rat model of analgesic nephropathy: effect of chloroquine.

The antimalaria drug chloroquine is often taken against a background of analgesic nephropathy caused by nonsteroidal anti-inflammatory drugs such as paracetamol (acetaminophen). Chloroquine has marked effects on the normal kidney and stimulates an increase in plasma vasopressin via nitric oxide. The aim of this study was to determine the renal action of chloroquine in a model of analgesic nephropathy.

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.

No effect on central or peripheral blood pressure of systemic urotensin II infusion in humans.

Aims: In rodent and primate studies, urotensin II is an extremely potent vasoconstrictor peptide with effects in the central aortic and arterial vasculature as well as on cardiac function. The aim of the present study was to assess systemic haemodynamic responses to intravenous urotensin II infusion in humans.

Methods: In 10 healthy male volunteers, intravenous urotensin II (3, 30 and 300 pmol min-1) and saline placebo were given on separate occasions in a single-blind randomized manner.

The effect of chloroquine on renal function and vasopressin secretion: a nitric oxide-dependent effect.

We have previously reported that chloroquine administration increases plasma vasopressin concentration and urinary sodium excretion in Sprague-Dawley rats. Because chloroquine has also been shown to stimulate nitric oxide production, the aim of this study was to determine whether nitric oxide mediates chloroquine-induced changes in renal function and secretion of vasopressin. Sprague-Dawley rats (n = 6-8/group) were infused with 2.

High plasma concentrations of human urotensin II do not alter local or systemic hemodynamics in man.

Objective: Human urotensin II (hUII) is an endocrine hormone that acts as a potent arterial vasoconstrictor in both in vitro and in vivo studies in animals. We examined, for the first time, the local and systemic hemodynamic response to hUII in man in vivo.

Methods: Four healthy male volunteers took part in pilot studies and 11 in definitive studies.

Cardiovascular actions of lungfish bradykinin in the unanaesthetised African lungfish, Protopterus annectens.

Bradykinin (BK) isolated from plasma of the African lungfish, Protopterus annectens, contains four amino acid substitutions compared with BK from mammals (Arg(1)-->Tyr, Pro(2)-->Gly, Pro(7)-->Ala, Phe(8)-->Pro). Bolus intra-arterial injections of synthetic lungfish BK (1-1000 pmol/kg body wt.) into unanaesthetised, juvenile lungfish (n=5) produced a dose-dependent increase in arterial blood pressure and pulse pressure.