Cloning and sequence analysis of cDNA encoding the precursor of a human endothelium-derived vasoconstrictor peptide, endothelin: identity of human and porcine endothelin

Differential activities of two distinct endothelin family peptides on ileum and coronary artery

A synthesized mouse vasoactive intestinal contractor peptide, which belongs to a novel member of the endothelin family, induced a prolonged contraction in mouse ileum as well as porcine coronary artery in vitro. Studies comparing the effects of vasoactive intestinal contractor and endothelin on different tissues revealed that the maximum ileum contraction of vasoactive intestinal contractor was much higher than that of endothelin in both guinea pig and mouse systems, but that the vasoconstriction activity of vasoactive intestinal contractor was weaker than that of endothelin in porcine artery. These results show that vasoactive intestinal contractor might be a novel gastrointestinal hormone.

Receptor binding activity and cytosolic free calcium response by synthetic endothelin analogs in cultured rat vascular smooth muscle cells

Using a variety of synthetic analogs of porcine endothelin (pET), we have studied the effects of these analogs on receptor binding activity and cytosolic free Ca2+ concentrations ([Ca2+]i) in cultured rat vascular smooth muscle cells (VSMC). Removal of C-terminal Trp21 residue, truncated derivatives pET(1-15) and (16-21), substitution of disulfide bond, Cys(3-11) or Cys(1-15), by Cys (Acm), all resulted in a complete loss of receptor binding activity and [Ca2+]i response, while N-terminal elongation of Lys-Arg residues, but not oxidation of Met7 residue, decreased receptor binding activity and [Ca2+]i response. [Cys1-15,Cys3-11]pET was far more potent than [Cys1-11,Cys3-15]pET in receptor binding and [Ca2+]i response. These data indicate that the C-terminal Trp21 as well as the proper double cyclic structure formed by the intramolecular disulfide bonds of the pET molecule are essential for receptor binding and subsequent [Ca2+]i increase in rat VSMC.

Putative precursors of endothelin have less vasoconstrictor activity in vitro but a potent pressor effect in vivo

Endothelin (ET-21) induced a sustained contraction of rat thoracic aortae (EC50 = 2.65 x 10(-10) M) in vitro, and caused a potent pressor effect in vivo after intravenous administration to rats. In contrast, the precursor deduced from porcine cDNA coding ET-21 (pET-39) had 100-fold less contractile activity in vitro (EC50 = 3.26 x 10(-8) M), and so did the precursor from human cDNA (hET-38) (EC50 = 1.48 x 10(-8) M). However, both pET-39 and hET-38 caused almost the same dose-dependent pressor effects as ET-21 in vivo. After intravenous bolus injection at 1 nmol/kg, ET-21 caused an initial transient drop of the arterial pressure, and then induced a gradual pressor effect. On the other hand, hET-38 caused only a gradual rise of the arterial pressure. There may be different mechanism(s) for ET-21 and hET-38 which induce changes in the arterial pressure in vivo.

Endothelin potentiates growth factor-stimulated DNA synthesis in Swiss 3T3 cells

A murine cell line, Swiss 3T3, is commonly used for the study of cellular growth. The present study revealed that this cell line possesses high-affinity receptors for endothelin, a vasoactive peptide derived from vascular endothelial cells. In this cell line, endothelin potentiated DNA synthesis stimulated by platelet-derived growth factor, basic fibroblast growth factor or insulin. The endothelin concentration required for potentiating DNA synthesis in this cell line is almost the same as that reported previously in endothelin-induced vasoconstriction. Since endothelin increased intracellular calcium levels, this ion may participate in the signal transduction pathways by which endothelin induces potentiation of DNA synthesis.

Cardiovascular actions of human endothelin in conscious sheep

1. Synthetic human endothelin was injected intravenously over the range 1.5-50 micrograms to examine its cardiovascular actions in conscious sheep. 2. Mean arterial pressure increased by 9-21 mmHg within 30-120 s over the range 5-50 micrograms endothelin. The increase in blood pressure was associated with increased calculated total peripheral resistance and a fall in cardiac output and heart rate. Stroke volume was increased. 3. Injection of endothelin into ganglion blocked sheep produced vasoconstriction and an increased blood pressure response associated with an attenuation of the effects on cardiac output, heart rate and stroke volume. 4. This study suggests that endothelin produces potent arterial vasoconstriction and reflex mediated effects on the heart in conscious sheep.

The human endothelin family: three structurally and pharmacologically distinct isopeptides predicted by three separate genes

Three distinct human endothelin-related genes were cloned by screening a genomic DNA library under a low hybridization stringency with a synthetic oligonucleotide probe encoding a portion of the endothelin sequence. Genomic Southern blot analysis with the same oligonucleotide probe showed three corresponding chromosomal loci not only in the human genome but also in porcine and rat genomes. The nucleotide sequences of the three human genes were highly conserved within the regions encoding the 21-residue (mature) endothelins, in spite of the fact that the immediately upstream exon sequences, which encode a part of the propeptides, retained little similarity. Moreover, each of the human genes predicted a putative 21-residue peptide, similar to but distinct from each other: (i) the "classical" endothelin (ET-1), (ii) [Trp6,Leu7]endothelin (ET-2), and (iii) [Thr2,Phe4,Thr5,Tyr6, Lys7,Tyr14]endothelin (ET-3). Synthetic ET-1, ET-2, and ET-3 were prepared according to the deduced amino acid sequences, and the biological activities were assayed by contraction of isolated porcine coronary artery strips and by intravenous injection to anesthetized rats. All these synthetic peptides produced strong vasoconstrictor and pressor responses. However, the quantitative profiles of the pharmacological activities were considerably different among the three isopeptides, suggesting the possible existence of endothelin receptor subtypes.

Endothelin and the production of cerebral vasospasm in dogs

We attempted to determine whether or not endothelin (ET) plays a physiological role in cerebral vasospasm. ET (10(-11) - 3 x 10(-8) M) induced a concentration-dependent contraction in isolated canine basilar arteries. Intracisternal injection of 10 to 1,000 pmol ET into dogs induced a dose-dependent decrease in the basilar artery diameter, as measured angiographically on the 1st day. On the 3rd day after the injection of ET (10 pmol), the diameter of the basilar artery had diminished to 76% of the value seen in the control. There were no effects on blood pressure or heart rate. Thus, ET seems to be a potent constrictor of cerebral arteries in vivo, and these effects are long-lasting.

A sensitive sandwich-enzyme immunoassay for human endothelin

A sensitive enzyme immunoassay (EIA) for human endothelin(1-21) has been established. The assay is based on a sandwich method that uses two differing capture and detection anti-endothelin antibodies. A monoclonal anti-endothelin antibody AwETN40, which did not react with an endothelin C-terminal heptapeptide, was used as an immobilized antibody. The Fab' fragment of rabbit antibodies against the endothelin C-terminal heptapeptide was used as an enzyme-labeled detector antibody after being coupled with horseradish peroxidase (HRP). The assay is sensitive enough to detect as little as 0.2 pg/well (80 amol/well) of endothelin. Preliminary investigations indicated that the basal level of immunoreactive endothelin in male plasma (n = 24) extracted with Seppak C-18 cartridges was 1.59 +/- 0.32 pg/ml.

Presence of immunoreactive endothelin in human plasma

A highly specific and sensitive radioimmunoassay has been established for measurement of human endothelin (hET) in human plasma. After extraction of plasma with an octyl-silica column, this assay allowed for detection of immunoreactive (IR) hET as low as 0.2 fmol/ml. In 16 healthy subjects, the mean concentration of plasma IR-hET was 0.6 fmol/ml. Reverse-phase HPLC coupled with radioimmunoassay revealed two major IR-hET components, one corresponding to authentic hET(1-21) and another with more hydrophilicity than hET(1-21). These data indicate that ET is a circulating vasoconstrictor hormone in man.

Endothelin stimulates phospholipase C, Na+/H+ exchange, c-fos expression, and mitogenesis in rat mesangial cells

A recently described peptide hormone, endothelin, is a potent vasoconstrictor, but it is unclear whether endothelin has other biological actions. These experiments extend the range of biological actions of endothelin to stimulation of mitogenesis. Endothelin at low concentrations (0.1-10 nM) induced mitogenesis by quiescent rat glomerular mesangial cells in culture. Mitogenesis induced by endothelin was accompanied by activation of phospholipase C with increased inositol phosphate turnover and increments of intracellular [Ca2+]. Endothelin also activated Na+/H+ exchange, causing cytosolic alkalinization, and enhanced transcription of the c-fos protooncogene, additional biochemical signals closely linked to proliferation. In addition to being a vasoconstrictor, endothelin thus also functions as a mitogen, presumably through activation of phospholipase C.

Endothelin action on vascular smooth muscle involves inositol trisphosphate and calcium mobilization

Cultured endothelial cells release a potent vasoconstrictor peptide, endothelin. Cumulative addition of synthetic endothelin to isolated rabbit aortic rings elicited a concentration-dependent increase in contractile tension which was endothelium-independent. In cultured rabbit vascular smooth muscle cells loaded with the fluorescent dye fura 2, endothelin induced a concentration-dependent increase in [Ca2+]i over the range of 0.01 to 100 nM. Moreover, in the absence of extracellular Ca2+, endothelin could still induce an increase in [Ca2+]i. In addition, endothelin stimulated 45Ca2+ efflux from preloaded vascular smooth muscle cells in the presence and absence of extracellular Ca2+, as well as stimulating 45Ca2+ influx in a concentration-dependent manner. Measurement of inositol phosphates in [3H]-myoinositol-labelled vascular vascular trisphosphate. Unlabelled endothelin inhibited (125I)-endothelin binding to cultured rabbit vascular smooth muscle cells in a concentration-dependent manner. Binding was not inhibited by other vasoactive hormones or calcium channel ligands, suggesting cell surface receptors specific for endothelin. We conclude that one of the initial membrane events in the action of endothelin is to induce phospholipase C-stimulated PIP2 hydrolysis and that this signalling mechanism is initiated by endothelin/receptor interaction at the plasma membrane.

Competitive interaction between endothelin and sarafotoxin: Binding and phosphoinositides hydrolysis in rat atria and brain

Binding studies with the structurally similar vasoconstrictor peptides 125I-endothelin and 125I-sarafotoxin b, the former of mammalian origin and the latter derived from snake venom, reveal their mutually exclusive binding to rat atrium and various regions of the rat brain. In these tissues endothelin, like sarafotoxin, induces phosphoinositide hydrolysis which is in part Ca2+-independent. It is suggested that endothelins and sarafotoxins share common binding sites and mechanisms of action.

Endothelin, its diverse biological activities and mechanisms of action

Endothelin, originally identified as a vasoconstrictive peptide derived from vascular endothelial cells, is now known to exert diverse biological effects on a wide variety of tissues and cell types through its own receptor(s). One of the outstanding actions of endothelin is a cell growth promoting activity which is demonstrated in several cell types including cultured vascular smooth muscle cells, fibroblasts, glomerular mesangial cells and osteoblasts. The mitogenic effect is likely mediated by stimulation of phospholipase C via receptor-G-protein coupling, and subsequent activation of protein kinase C. The effect of endothelin may contribute to the cell-proliferation response under various physiological and pathological conditions, such as wound healing and development of atherosclerosis and glomerulonephritis. Recently, three distinct endothelin-related genes have been cloned, suggesting that mammals, including humans, produce three members of this peptide family, endothelin (ET)-1 (the 'classical' endothelin), ET-2 and ET-3, which may act on distinct subtypes of endothelin receptor to induce different cellular responses.

Endothelin--a new family of endothelium-derived peptides with widespread biological properties

Endothelin (ET) is a novel family of three isopeptides (ET-1, ET-2, ET-3) each containing twenty-one amino acids and two disulfide bonds. Initially isolated from the supernatant of cultured porcine aortic endothelial cells, ET is stored as a preproform and released through an unusual proteolytic cleavage. In general, ET-1, ET-2, ET-3 differ quantitatively but not qualitatively in their biologic activity. ET have potent contractile activity in a variety of isolated tissues including arteries veins, trachea, duodenum urinary bladder and uterus. In vivo, ET possesses potent vasodilator and vasoconstrictor properties. Although the mechanisms mediating the hemodynamic effects of ET are not entirely clarified, recent evidence indicates a role for endothelium-derived relaxant factor (EDRF), protein kinase C and extracellular calcium. Moreover, ET appears to produce inflammation and bronchoconstriction through the formation of arachidonic acid metabolites via the cyclooxygenase pathway. The presence of ET binding sites in blood vessels and in several organ systems suggests ET may have important regulatory functions, which remain to be determined.

Endothelin stimulates release of atrial natriuretic peptides in vitro and in vivo

The effect of endothelin (END) on the release of atrial natriuretic peptides (ANP) was studied in isolated rat atria and in conscious rats. END stimulates the ANP release in vitro in a dose-dependent manner. An increase in ANP plasma levels and cyclic GMP plasma levels was also observed in conscious rats after injection of END. When a monoclonal antibody directed against ANP was injected together with END the increase in cyclic GMP was completely blocked. From this study it is concluded that END is a potent secretagogue for ANP both in vitro and in vivo.

Specific receptors for endothelin on membranes from human placenta. Characterization and use in a binding assay

High-affinity binding sites for endothelin have been found in a human placenta membrane preparation. 125I-endothelin bound to placenta membranes at 20 degrees C with an association half-time of 30 min, whereas the binding was only slowly reversed with a dissociation half-time of 250 min. In saturation experiments, a single class of high-affinity binding sites was identified with an apparent dissociation constant (KD) of 24 pM and a maximal density of 240 fmol per mg of protein. The binding of 125I-endothelin was half-maximally inhibited by cold endothelin at a concentration (IC50) of 140 pM. In contrast, no inhibition was found at 10(-4) M for a variety of vasoactive peptides such as angiotensin II, vasopressin, neuropeptide Y, substance P, CGRP, bradykinin, leucine enkephalin or dynorphin A. Similarly, the binding was modulated neither by the calcium channel blockers nifedipine, verapamil or diltiazem, nor by the calcium channel agonist Bay k 8644. There was also no effect with the structurally-related bee venom apamin. Using this membrane preparation, endothelin-like activity could be measured in the medium of cultured human endothelial cells by competition binding technique.

Hemodynamic actions of endothelin in conscious and anesthetized dogs

The newly described endogenous peptide, endothelin, was administered to five chronically instrumented conditioned dogs. Endothelin produced significant and simultaneous increases in both heart rate (HR) and mean arterial pressure (MAP) in conscious dogs. Endothelin also produced significant increases in MAP in anesthetized animals. Ganglionic suppression induced by hexamethonium (10 mg/kg) and atropine (0.1 mg/kg) blocked HR responses and markedly inhibited the pressor responses to endothelin in conscious animals. These results suggest that endothelin in part acts to elevate blood pressure and heart rate through modification of autonomic nervous system tone. When endothelin and angiotensin II were administered in mole equivalent doses, angiotensin II produced a pressor response of greater magnitude than did endothelin in conscious animals.

Endothelin: a new inhibitor of renin release

Endothelin is a recently-discovered vasoconstrictor peptide which is produced by endothelium and acts on vascular smooth muscle cells. At present its actions on other organs or cells are unknown. We studied the effect of endothelin on renin release in a dynamic superfusion system of dispersed rat juxtaglomerular (JG) cells. Endothelin in concentrations of 10(-11) M or more inhibited renin release dose-dependently and this inhibitory action vanished in the absence of extracellular Ca. It is suggested that endothelin is an inhibitory regulator of renin secretion from JG cells and its action is Ca-dependent.

Molecular mechanism of action of the vasoconstrictor peptide endothelin

Endothelin, one of the most potent vasoconstrictor known, has been suggested to act as an endogenous agonist of L-type Ca2+ channels. In this paper we show that endothelin stimulates the metabolism of inositol phosphates and induces the mobilization of intracellular Ca2+ stores. The transient activation of Ca2+-sensitive K+ channel provokes an hyperpolarization of the membrane. It is followed by a sustained depolarization which is due to the opening of a non-specific cation channel which is permeable to Ca2+ and Mg2+. The depolarization then activates L-type Ca2+ channels. This mechanism of action explains why part of the endothelin-induced vasocontriction is eliminated by L-type Ca2+ channel blockers.

Synthesis and disulfide structure determination of porcine endothelin: an endothelium-derived vasoconstricting peptide

All disulfide analogs (types A, B and C) of porcine or human endothelin, a 21-amino acid peptide having two intramolecular disulfide bonds, were synthesized and their retention times on HPLC were compared with that of natural endothelin. One of the analogs (type A) having disulfide bonds between positions 1 and 15 and between 3 and 11 was found to be identical with natural endothelin. Random oxidation of fully reduced endothelin formed a mixture of type A and B in a ratio of 3:1, with almost none of type C, which has disulfide bonds between positions 1 and 3 and between 11 and 15. Type A endothelin was also synthesized by the segment condensation procedure in solution applying our maximum protection strategy. This product was found to have full vasoconstricting activity in rat pulmonary artery ring preparations; the potency was as high as that of the natural product.

Structure-activity relationships of endothelin: importance of the C-terminal moiety

The vasoconstrictor activities of various forms of derivatives of endothelin (ET) were characterized in vitro by measuring the contraction of porcine coronary artery strips. The removal of the C-terminal Trp21 reduced the molar potency of the peptide by nearly 3 orders of magnitude. The removal of amino acid residues from the C-terminus of ET(1-20) further attenuated the activity. Replacement of Trp21 with D-Trp, reduction and carboxamidomethylation of the four Cys residues, or cleavage at Lys9 by lysyl endopeptidase all lowered the potency approximately 200 fold. While both native ET and [D-Trp21]ET induced a very slow and sustained vasoconstriction, the other derivatives of ET listed above showed a much more rapid kinetics of vasoconstriction. These results indicate that the C-terminal Trp of ET is especially important for the potent and extremely long-lasting vasoconstrictor activity characteristic to ET.

Positive chronotropic effects of endothelin, a novel endothelium-derived vasoconstrictor peptide

Endothelin (ET) is a novel 21-amino-acid peptide isolated from the culture supernatant of porcine aortic endothelial cells, which has a potent vasoconstricting effect. It has been suggested that ET increases Ca2+ influx via a voltage-dependent Ca2+ channel. The purpose of the present study is to investigate the mode of actions of ET on the cardiac automaticity. ET increased the sinoatrial nodal rate in a dose-dependent manner on the isolated right atria of guinea pigs. The positive chronotropic effect of ET was very potent and the ED50 value was 0.4 nM. These results suggest that ET is one of the most potent cardio-acceleratory substances.

Does endothelin mobilize calcium from intracellular store sites in rat aortic vascular smooth muscle cells in primary culture?

In the presence of endothelin, there was a rapid increase in the 45Ca++ efflux from primary cultured rat vascular smooth muscle cells, both in physiological salt solution and in calcium free medium containing 2 mM EGTA. The 45Ca++ influx was not affected. The endothelin-induced, transient increase in cytosolic calcium concentration is probably mainly due to release of calcium from the intracellular store in vascular smooth muscle cells.

Primary structure, synthesis, and biological activity of rat endothelin, an endothelium-derived vasoconstrictor peptide

Endothelin is a potent vasoconstrictor/pressor peptide, which we recently characterized from the conditioned culture medium of porcine aortic endothelial cells. We report here the cloning and partial sequencing of the rat endothelin gene. The nucleotide sequence predicted a 21-residue peptide similar to, but distinct from, porcine endothelin; 15 residues of rat endothelin were identical and 3 residues were substitutions by chemically similar amino acid residues to those in the porcine peptide. Synthetic rat endothelin was then prepared according to its deduced amino acid sequence. This synthetic peptide had (i) potent vasoconstrictor activity in the rat aortic strip and in perfused rat heart and (ii) a characteristically long-lasting in vivo pressor activity by intraaortic bolus injection in the conscious rat.