Comparison of the contractile responses of human coronary bypass grafts and monkey arteries to human urotensin-II

Natural and synthetic peptides in the cardiovascular diseases: An update on diagnostic and therapeutic potentials

Several peptides play an important role in physiological and pathological conditions into the cardiovascular system. In addition to well-known vasoactive agents such as angiotensin II, endothelin, serotonin or natriuretic peptides, the vasoconstrictor Urotensin-II (Uro-II) and the vasodilators Urocortins (UCNs) and Adrenomedullin (AM) have been implicated in the control of vascular tone and blood pressure as well as in cardiovascular disease states including congestive heart failure, atherosclerosis, coronary artery disease, and pulmonary and systemic hypertension. Therefore these peptides, together with their receptors, become important therapeutic targets in cardiovascular diseases (CVDs). Circulating levels of these agents in the blood are markedly modified in patients with specific CVDs compared with those in healthy patients, becoming also potential biomarkers for these pathologies. This review will provide an overview of current knowledge about the physiological roles of Uro-II, UCN and AM in the cardiovascular system and their implications in cardiovascular diseases. It will further focus on the structural modifications carried out on original peptide sequences in the search of analogues with improved physiochemical properties as well as in the delivery methods. Finally, we have overviewed the possible application of these peptides and/or their precursors as biomarkers of CVDs.

The role of urotensin II and atherosclerotic risk factors in patients with slow coronary flow

BACKGROUND

Slow coronary flow (SCF) is an angiographic finding characterized with delayed opacification of epicardial coronary arteries without obstructive coronary disease. Urotensin II (UII) is an important vascular peptide, which has an important role in hypertension, coronary artery disease, and vascular remodeling in addition to potent vasoconstrictor effect.

OBJECTIVES

We investigated UII levels, hypertension, and other atherosclerotic risk factors in patients with SCF, a variety of coronary artery disease.

METHODS

We enrolled 14 patients with SCF and 29 subjects with normal coronary arteries without SCF. We compared the UII levels and the atherosclerotic risk factors between patients with SCF and control subjects with normal coronary flow.

RESULTS

UII concentrations were significantly higher in patients with SCF compared to controls (711.0 ± 19.4 vs. 701.5 ± 27.2 ng/mL, p = 0.006). We detected a positive correlation between SCF and age (r = 0.476, p = 0.001), BMI (r = 0.404, p = .002), UII concentrations (r = 0.422, p = 0.006), and hypertension (r = 0.594, p = 0.001).

CONCLUSION

We identified increased UII levels in patients with SCF. We think that UII concentrations may be informative on SCF pathogenesis due to relationship with inflammation, atherosclerosis, and vascular remodeling.

International Union of Basic and Clinical Pharmacology. XCII. Urotensin II, urotensin II-related peptide, and their receptor: from structure to function

Urotensin II (UII) is a cyclic neuropeptide that was first isolated from the urophysis of teleost fish on the basis of its ability to contract the hindgut. Subsequently, UII was characterized in tetrapods including humans. Phylogenetic studies and synteny analysis indicate that UII and its paralogous peptide urotensin II-related peptide (URP) belong to the somatostatin/cortistatin superfamily. In mammals, the UII and URP genes are primarily expressed in cholinergic neurons of the brainstem and spinal cord. UII and URP mRNAs are also present in various organs notably in the cardiovascular, renal, and endocrine systems. UII and URP activate a common G protein-coupled receptor, called UT, that exhibits relatively high sequence identity with somatostatin, opioid, and galanin receptors. The UT gene is widely expressed in the central nervous system (CNS) and in peripheral tissues including the retina, heart, vascular bed, lung, kidney, adrenal medulla, and skeletal muscle. Structure-activity relationship studies and NMR conformational analysis have led to the rational design of a number of peptidic and nonpeptidic UT agonists and antagonists. Consistent with the wide distribution of UT, UII has now been shown to exert a large array of biologic activities, in particular in the CNS, the cardiovascular system, and the kidney. Here, we review the current knowledge concerning the pleiotropic actions of UII and discusses the possible use of antagonists for future therapeutic applications.

Circulating levels of the vasoactive peptide urotensin II in patients with acute coronary syndrome and stable coronary artery disease

Urotensin II (UII) is a vasoactive peptide with various roles in cardiovascular physiology and pathophysiology. There is an accumulating evidence implicating UII in atherosclerosis and coronary artery disease, making it an important target in acute coronary syndrome (ACS). In this study, we sought to determine the plasma levels of UII in ACS patients within 48 h of clinical presentation and after a 12-week recovery period. We compared them to patients with stable coronary artery disease (CAD) and a control group of normolipidemic subjects without known CAD. Using a highly sensitive ELISA technique, we measured plasma UII in 27 ACS patients, 26 stable CAD patients and 22 age-matched controls. ACS patients had significantly elevated plasma UII during the first 48 h of clinical presentation compared to stable CAD patients and controls. We also found significant positive correlations between UII and CRP and with triglycerides and a significant negative correlation between UII and EF. There was no correlation with LDL-C. In conclusion, plasma UII levels were elevated in patients with acute coronary syndrome, particularly immediately after clinical presentation. This suggests an upregulation of UII expression in ACS.

The interaction between human urotensin II and vasodilator agents in human internal mammary artery with possible clinical implications

BACKGROUND

Graft spasm in the internal mammary artery (IMA) may occur after coronary artery bypass grafting (CABG). We investigated the effect of human urotensin II (hU-II), a cyclic peptide hormone present in human blood and tissues, and the effect of vasodilators on hU-II-mediated response in human IMA.

METHODS

Fresh IMA segments (n=114) taken from 50 patients undergoing CABG were studied in a myograph. The interaction between hU-II and various calcium antagonists or glyceryl trinitrate (GTN) was investigated in 2 ways: relaxing effect of vasodilators on the hU-II-induced precontraction and depressing effect of vasodilator agents on the contraction caused by hU-II (n=6 to 10 in each subgroup).

RESULTS

Human urotensin II caused contractile response in all human IMA. In potassium chloride-contraction, full (nifedipine: 99.1 %±2.7%) or nearly full (diltiazem: 93.5%±4.8%) relaxation with 30.9-fold higher potency to nifedipine than to diltiazem (EC50 [effective concentration causing 50% of maximal response] -8.24±0.21 vs -6.75±0.20 log M, p=0.0002) and in hU-II-contraction, nearly full relaxation (nifedipine: 90.6%±4.6%; diltiazem: 95.0%±1.7%) with 5.8-fold higher potency to nifedipine than to diltiazem (EC50 -7.55±0.26 vs -6.79±0.25 log M, p=0.03) were observed. The GTN caused nearly full relaxation (93.1%±4.8%) but GTN pretreatment had limited effect in prevention of the hU-II-induced contraction, whereas diltiazem and nifedipine reduced subsequent contraction to hU-II.

CONCLUSIONS

Human urotensin II is a potent vasoconstrictor in human IMA. Calcium antagonists and GTN relax the contraction caused by hU-II with different potencies. However, calcium antagonists are more effective than GTN in preventing the contraction induced by hU-II. These findings may have clinical implications in CABG.

Urotensin II: a new pharmacologic target in the treatment of cardiovascular disease

Urotensin II was first identified over 30 years ago as a potent vasoconstrictor, and the identification of its receptor in the heart, lungs, blood vessels, and brain have made it a potential target for human pharmacotherapy. Current research would suggest that urotensin II plays a major role in the pathophysiology of various cardiovascular disease entities. This article discusses the biologic effects of urotensin under normal and pathophysiologic conditions, and reviews the research experiences with synthetic urotensin blockers in the treatment of various cardiovascular illnesses.

Immunocytochemical localization of the urotensin-II receptor, UT, to rat and human tissues: relevance to function

We have examined whether differential expression of UT receptors in cardiovascular tissues from rats and humans may account for the diverse vascular actions reported for urotensin-II. We found UT immunoreactivity ubiquitously expressed in arterial and venous smooth muscle and cardiomyocytes in both species, however, compared to human, levels of UT immunoreactivity in rat vascular endothelial cells was below the level for detection. In rat skeletal muscle cells UT receptor localized to the sarcolemma, a pattern comparable to that for isoforms of nitric oxide synthase suggesting that urotensin-II mediated hindquarter vasodilatation may involve release of nitric oxide from skeletal muscle fibers.

Cardiorenovascular effects of urotensin II and the relevance of the UT receptor

Urotensin II (U-II) is a vasoactive peptide with many potent effects in the cardiorenovascular system. U-II activates a G-protein-coupled receptor termed UT. UT and U-II are highly expressed in the cardiovascular and renal system. Patients with various cardiovascular diseases show high U-II plasma levels. It was demonstrated that elevated U-II plasma levels and increased UT expression seem to play a role in heart failure, end-stage renal disease and atherosclerosis. U-II induces potent changes in vascular tone regulation. In addition, U-II stimulates vascular smooth muscle cell proliferation and cardiomyocyte hypertrophy. Currently several pharmaceutical companies are developing compounds to control the U-II/UT system. There are preclinical and some clinical studies showing potential benefits of inhibiting U-II function in renal disease, heart failure, and diabetes. This article will review both pre- and clinical data concerning cardiorenovascular effects of U-II.

Human urotensin II as a link between hypertension and coronary artery disease

Hypertension is a well-known risk factor for atherosclerosis, but the molecular mechanisms that link elevated blood pressure to the progression of atherosclerosis remain unclear. Human urotensin II (U-II), the most potent endogenous vasoconstrictor peptide identified to date, and its receptor (UT receptor) are involved in the etiology of essential hypertension. In patients with essential hypertension, U-II infused into the forearm brachial artery has been shown to induce vasoconstriction. Recent studies have demonstrated elevated plasma U-II concentrations in patients with essential hypertension, diabetes mellitus, atherosclerosis, and coronary artery disease. U-II is expressed in endothelial cells, macrophages, macrophage-derived foam cells, and myointimal and medial vascular smooth muscle cells (VSMCs) of atherosclerotic human coronary arteries. UT receptors are present in VSMCs of human coronary arteries, the thoracic aorta and cardiac myocytes. Lymphocytes are the most active producers of U-II, whereas monocytes and macrophages are the major cell types expressing UT receptors, with relatively little receptor expression in foam cells, lymphocytes, and platelets. U-II accelerates foam cell formation by up-regulation of acyl-coenzyme A:cholesterol acyltransferase-1 in human monocyte-derived macrophages. In human endothelial cells, U-II promotes cell proliferation and up-regulates type 1 collagen expression. U-II also activates nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and plasminogen activator inhibitor-1 in human VSMCs, and stimulates VSMC proliferation with synergistic effects observed when combined with oxidized low-density lipoprotein, lysophosphatidylcholine, reactive oxygen species or serotonin. These findings suggest that U-II plays key roles in accelerating the development of atherosclerosis, thereby leading to coronary artery disease.

Nonpeptidic urotensin-II receptor antagonists I: in vitro pharmacological characterization of SB-706375

1. SB-706375 potently inhibited [(125)I]hU-II binding to both mammalian recombinant and 'native' UT receptors (K(i) 4.7+/-1.5 to 20.7+/-3.6 nM at rodent, feline and primate recombinant UT receptors and K(i) 5.4+/-0.4 nM at the endogenous UT receptor in SJRH30 cells). 2. Prior exposure to SB-706375 (1 microM, 30 min) did not alter [(125)I]hU-II binding affinity or density in recombinant cells (K(D) 3.1+/-0.4 vs 5.8+/-0.9 nM and B(max) 3.1+/-1.0 vs 2.8+/-0.8 pmol mg(-1)) consistent with a reversible mode of action. 3. The novel, nonpeptidic radioligand [(3)H]SB-657510, a close analogue of SB-706375, bound to the monkey UT receptor (K(D) 2.6+/-0.4 nM, B(max) 0.86+/-0.12 pmol mg(-1)) in a manner that was inhibited by both U-II isopeptides and SB-706375 (K(i) 4.6+/-1.4 to 17.6+/-5.4 nM) consistent with the sulphonamides and native U-II ligands sharing a common UT receptor binding domain. 4. SB-706375 was a potent, competitive hU-II antagonist across species with pK(b) 7.29-8.00 in HEK293-UT receptor cells (inhibition of [Ca(2+)](i)-mobilization) and pK(b) 7.47 in rat isolated aorta (inhibition of contraction). SB-706375 also reversed tone established in the rat aorta by prior exposure to hU-II (K(app) approximately 20 nM). 5. SB-706375 was a selective U-II antagonist with >/=100-fold selectivity for the human UT receptor compared to 86 distinct receptors, ion channels, enzymes, transporters and nuclear hormones (K(i)/IC(50)>1 microM). Accordingly, the contractile responses induced in isolated aortae by KCl, phenylephrine, angiotensin II and endothelin-1 were unaltered by SB-706375 (1 microM). 6. In summary, SB-706375 is a high-affinity, surmountable, reversible and selective nonpeptide UT receptor antagonist with cross-species activity that will assist in delineating the pathophysiological actions of U-II in mammals.

Urotensin-II and the cardiovascular system – the importance of developing modulators

Urotensin-II (U-II) potently contracts some large isolated blood vessels and cardiac tissue. However, the maximum effects on human blood vessels and heart are relatively small. U-II dilates human resistance arteries. It markedly decreased myocardial function and increased vascular resistance in cynomolgus monkeys, but the major effects of U-II have not been observed in healthy humans. A major role for U-II in human cardiovascular disease has not been clearly established despite studies in patients with coronary artery disease, heart failure, essential hypertension and diabetes. Peptide and non-peptide agonists and antagonists of the U-II receptor are being developed and will be useful in the characterisation of the effects of U-II, and may have some therapeutic potential.

Urotensin II in the cardiovascular system

Urotensin II is a peptide present, together with its receptor, in the central nervous system and many peripheral tissues (including heart, blood vessels, kidneys and endocrine organs) of many species. The bioactive, mature form contains a cyclic heptapeptide perfectly preserved across species spanning 550 million years of evolution Its biological activity has been explored in cultured cells, in isolated vessels from several species, in the isolated perfused heart and in intact animals and man. Initial demonstration of potent vasoconstriction and cardiac depression by the human isoform in non-human primates has been followed by a series of reports indicating potent but highly variable and generally modest vascular responses dependent on species and vascular region. In man short term cardiovascular responses to administered urotensin II are small or absent. The place of urotensin II in the chronic trophic responses to cardiac and vascular injury and its possible roles as a neurotransmitter and/or regulator of renal and endocrine function remain largely unexplored.

Urotensin II and cardiovascular diseases

Urotensin II (UII) has been found to be a potent vasoactive peptide in humans and in a number of relevant animal models of cardiovascular disease such as the mouse, rat and other non-human primates. This peptide with structural homology to somatostatin was first isolated from the urophysis of fish and was recently found to bind to an orphan receptor in mouse and human. Initially found to have potent vasoconstrictive activities in a variety of vessels from diverse species, it has also been shown to exert vasodilatation in certain vessels in the rat and human by various endothelium-dependent mechanisms. The various vasoactive properties of UII suggest that the peptide may have a physiological role in maintaining vascular tone and therefore may have a role in the pathophysiology of a number of human diseases such as heart failure. Moreover, UII has also been implicated as a mitogen of vascular smooth muscle cells suggesting a deleterious role in atherosclerosis and coronary artery disease. In addition, there is evidence to demonstrate that UII has multiple metabolic effects on cholesterol metabolism, glycemic control and hypertension and therefore may be implicated in the development of insulin resistance and the metabolic syndrome.

Emerging roles of urotensin-II in cardiovascular disease

Urotensin-II (UII) is a highly potent endogenous peptide within the cardiovascular system. Through stimulation of Galphaq-coupled UT receptors, UII mediates contraction of vascular smooth muscle and endothelial-dependent vasorelaxation, and positive inotropy in human right atrium and ventricle. A pathogenic role of the UT receptor system is emerging in cardiovascular disease states, with evidence for up-regulation of the UT receptor system in patients with congestive heart failure (CHF), pulmonary hypertension, cirrhosis and portal hypertension, and chronic renal failure. In vitro and in vivo studies show that under pathophysiological conditions, UII might contribute to cardiomyocyte hypertrophy, extracellular matrix production, enhanced vasoconstriction, vascular smooth muscle cell hyperplasia, and endothelial cell hyper-permeability. Single nucleotide polymorphisms of the UII gene may also impart a genetic predisposition of patients to diabetes. Therefore, the UT receptor system is a potential therapeutic target in the treatment of cardiac, pulmonary, and renal diseases. UT receptor antagonists are currently being developed to prevent and/or reverse the effects of over-activated UT receptors by the endogenous ligand. This review describes UII peptide and converting enzymes, and UT receptors in the cardiovascular system, focusing on pathophysiological roles of UII in the heart and blood vessels.

Techniques: Cardiovascular pharmacology and drug discovery in the 21st century

The latter half of the 20th century has been characterized by pharmacologists as the 'age of the receptor', an era in which the bioassay, that stalwart of classical pharmacology, has played a seminal role in identifying novel cardiovascular medicines. In this article, we ask what, if anything, has changed in the pharmacologist's approach to discovering novel cardiovascular drugs on this, the 25th anniversary of the inaugural publication of Trends in Pharmacological Sciences.

Urotensin-II: a novel systemic hypertensive factor in the cat

Urotensin-II, a potent mammalian vasoconstrictor, may play a role in the etiology of essential hypertension. However, a species suitable for assessing such a role, one where a "classical" systemic hypertensive response (increase in mean blood pressure and systemic vascular resistance) is observed following bolus i.v. urotensin-II administration, has yet to be identified. The present study demonstrates that the cat may represent such a species since urotensin-II potently (pEC(50)s 9.68+/-0.24-8.73+/-0.08) and efficaciously (E(max) 73+/-15%-205+/-21% KCl) constricts all feline isolated arteries studied (aortae, renal, femoral, carotid, and mesenteric conduit/resistance). Accordingly, exogenous urotensin-II (1 nmol/kg, i.v.) effectively doubles both mean blood pressure (from 99+/-14 to 183+/-15 mmHg) and systemic vascular resistance (from 0.36+/-0.12 to 0.86+/-0.20 mmHg/ml/min) in the anaesthetized cat (without altering heart rate or stroke volume). Thus, in view of these profound contractile effects, the cat could be suitable for determining the effects of urotensin-II receptor antagonism on cardiovascular homeostasis in both normal and diseased states.

Identification of urotensin II-related peptide as the urotensin II-immunoreactive molecule in the rat brain

Urotensin II (UII) has been reported as the most potent known vasoconstrictor. While rat and mouse orthologs of UII precursor protein have been reported, only the tentative structures of UII peptides of these animals have been demonstrated, since prepro-UII proteins lack typical processing sites for their mature peptides. In the present study, we isolated a novel peptide, UII-related peptide (URP), from the extract of the rat brain as the sole immunoreactive substance to anti-UII antibody; the amino acid sequence of the peptide was determined as ACFWKYCV. cDNAs encoding rat, mouse, and human precursor proteins for URP were cloned and revealed that the sequences of mouse and human URP peptides are the same as that for rat URP. Prepro-URP gene is expressed in several rat tissues such as those of the thymus, spleen, testis, and spinal cord, although with lower levels than the prepro-UII gene. In the human, the prepro-URP gene is expressed comparably to prepro-UII in several tissues except the spinal cord. URP was found to bind and activate the human or rat UII receptors (GPR14) and showed a hypotensive effect when administered to anesthetized rats. These results suggest that URP is the endogenous and functional ligand for UII receptor in the rat and mouse, and possibly in the human. We also describe the preparation of specific monoclonal antibodies raised against UII peptide and the establishment of a highly sensitive enzyme immunoassay system for UII peptides.

Functional and binding characterizations of urotensin II-related peptides in human and rat urotensin II-receptor assay

Urotensin II (U-II; cyclo5-10[H-Glu-Thr-Pro-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH]) is a potent vasoconstrictor in mammals, and it is postulated that it plays a central role in cardiovascular homeostasis. Thus, we initiated a structure-to-function analysis of this peptide characterized by a N-terminal tail and a cyclic core formed through a disulfide bridging. A total of 41 analogs focusing on these characteristics were developed and evaluated using a binding assay on membranes from a stable HEK-293 cell line containing the human or rat U-II receptor, a functional assay for Ca2+ mobilization on transiently transfected CHO-K1 cells with the human or rat U-II receptor, and a rat thoracic aorta bioassay. At first, the focus was applied on peptide compounds containing exocyclic modifications. From this series, it appeared that only valine-11 played a significant role although it is not an essential amino acid. Similarly, endocyclic and ring transformations of hU-II were also studied. In most cases, a detrimental effect on affinity and biological activity was observed. However, two compounds, [Tyr6]hU-II and [Phe9]hU-II, retained affinity and activity. So far, our binding, functional, and pharmacological data clearly demonstrated the minor contribution of the N-terminal segment and the essential role of the cyclic structure. More particularly, three residues within the loop, i.e., Trp-7, Lys-8, and Tyr-9, are required for receptor recognition and activation. This three-pole feature, kept by the disulfide bond in a correct spatial arrangement, appears as the key pharmacophore for the U-II receptor.

Deletion of the UT receptor gene results in the selective loss of urotensin-II contractile activity in aortae isolated from UT receptor knockout mice

1 Urotensin-II (U-II) is among the most potent mammalian vasoconstrictors identified and may play a role in the aetiology of essential hypertension. Currently, only one mouse U-II receptor (UT) gene has been cloned. It is postulated that this protein is solely responsible for mediating U-II-induced vasoconstriction. 2 This hypothesis has been investigated in the present study, which assessed basal haemodynamics and vascular reactivity to hU-II in wild-type (UT((+/+))) and UT receptor knockout (UT((-/-))) mice. 3 Basal left ventricular end-diastolic and end-systolic volumes/pressures, stroke volumes, mean arterial blood pressures, heart rates, cardiac outputs and ejection fractions in UT((+/+)) mice and in UT((-/-)) mice were similar. 4 Relative to UT((+/+)) mouse isolated thoracic aorta, where hU-II was a potent spasmogen (pEC(50)=8.26+/-0.08) that evoked relatively little vasoconstriction (17+/-2% 60 mM KCl), vessels isolated from UT((-/-)) mice did not respond to hU-II. However, in contrast, the superior mesenteric artery isolated from both the genotypes did not contract in the presence of hU-II. Reactivity to unrelated vasoconstrictors (phenylephrine, endothelin-1, KCl) and endothelium-dependent/independent vasodilator agents (carbachol, sodium nitroprusside) was similar in the aorta and superior mesenteric arteries isolated from both the genotypes. 5 The present study is the first to directly link hU-II-induced vasoconstriction with the UT receptor. Deletion of the UT receptor gene results in loss of hU-II contractile action with no 'nonspecific' alterations in vascular reactivity. However, as might be predicted based on the limited contractile efficacy recorded in vitro, the contribution that hU-II and its receptor make to basal systemic haemodynamics appears to be negligible in this species.

The neuromedin B receptor antagonist, BIM-23127, is a potent antagonist at human and rat urotensin-II receptors

The functional activity of the peptidic neuromedin B receptor antagonist BIM-23127 was investigated at recombinant and native urotensin-II receptors (UT receptors). Human urotensin-II (hU-II) promoted intracellular calcium mobilization in HEK293 cells expressing the human UT (hUT) or rat UT (rUT) receptors with pEC(50) values of 9.80+/-0.34 (n=6) and 9.06+/-0.32 (n=4), respectively. While BIM-23127 alone had no effect on calcium responses in either cell line, it was a potent and competitive antagonist at both hUT (pA(2)=7.54+/-0.14; n=3) and rUT (pA(2)=7.70+/-0.05; n=3) receptors. Furthermore, BIM-23127 reversed hU-II-induced contractile tone in the rat-isolated aorta with a pIC(50) of 6.66+/-0.04 (n=4). In conclusion, BIM- 23127 is the first hUT receptor antagonist identified to date and should not be considered as a selective neuromedin B receptor antagonist.

Pharmacological characterization of SB-710411 (Cpa-c[D-Cys-Pal-D-Trp-Lys-Val-Cys]-Cpa-amide), a novel peptidic urotensin-II receptor antagonist

1. Human urotensin-II (hU-II), a cyclic undecapeptide, is amongst the most potent mammalian vasoconstrictors identified, suggesting that hU-II and its G-protein-coupled receptor (UT) may regulate cardiovascular homeostasis. Such a hypothesis would benefit greatly from the development of selective UT antagonists. 2. Although the somatostatin (SST) antagonist SB-710411 (Cpa-c[D-Cys-Pal-D-Trp-Lys-Val-Cys]-Cpa-amide) is purported to block U-II-induced contractions in rat isolated aorta, little is known about its specific pharmacological properties. 3. SB-710411 (10 micro M) inhibited hU-II-induced contraction in rat isolated aorta causing a significant, parallel shift in the agonist concentration-response curve (pK(b) 6.28+/-0.11; n=8) with no suppression of the E(max). In contrast, SB-710411 did not alter the contractile actions of angiotensin-II, phenylephrine, or KCl. Paradoxically, however, SB-710411 potentiated the contractile response to endothelin-1 (pEC(50) 8.02+/-0.16 and 8.54+/-0.11, P<0.01; n=8). Rather than being specific toSB-710411, this phenomenon appears to be related to somatostatin receptor affinity and not intrinsic activity since the SST agonist somatostatin-14 and antagonist cyclo-somatostatin also potentiated endothelin-1-induced contraction. 4. SB-710411 (10 micro M) did not inhibit carbachol, sodium nitroprusside, IBMX, isoprenaline, and levcromakalim-induced reversal of tone established with noradrenaline. In contrast, however, SB-710411 significantly inhibited the reversal of tone established with endothelin-1 using the same vasorelaxants. 5. In summary, although SB-710411 inhibits the vasoconstrictor actions of hU-II in a competitive, surmountable manner, it also possesses additional pharmacological actions. Thus, whilst the present study is amongst the first to detail the properties of a functional U-II receptor antagonist, the data suggest caution be used when assessing data generated utilizing this moiety and other SST analogues.

Magnifying endoscopic observation of the gastric mucosa, particularly in patients with atrophic gastritis

The gastric mucosal surface was observed using the magnifying fibergastroscope (FGS-ML), and the fine gastric mucosal patterns, which were even smaller than one unit of gastric area, were examined at a magnification of about 30. For simplicification, we classified these patterns by magnifying endoscopy in the following ways; FP, FIP, FSP, SP and MP, modifying Yoshii's classification under the dissecting microscope. The FIP, which was found to have round and long elliptical gastric pits, is a new addition to our endoscopic classification. The relationship between the FIP and the intermediate zone was evaluated by superficial and histological studies of surgical and biopsy specimens. The width of the band of FIP seems to be related to the severity of atrophic gastritis. Also, the transformation of FP to FIP was assessed by comparing specimens taken from the resected and residual parts of the stomach, respectively. Moreover, it appears that severe gastritis occurs in the gastric mucosa which shows a FIP. Therefore, we consider that the FIP indicates the position of the atrophic border.

Magnifying endoscopic observation of the gastric mucosa, particularly in patients with atrophic gastritis

The gastric mucosal surface was observed using the magnifying fibergastroscope (FGS-ML), and the fine gastric mucosal patterns, which were even smaller than one unit of gastric area, were examined at a magnification of about 30. For simplicification, we classified these patterns by magnifying endoscopy in the following ways; FP, FIP, FSP, SP and MP, modifying Yoshii's classification under the dissecting microscope. The FIP, which was found to have round and long elliptical gastric pits, is a new addition to our endoscopic classification. The relationship between the FIP and the intermediate zone was evaluated by superficial and histological studies of surgical and biopsy specimens. The width of the band of FIP seems to be related to the severity of atrophic gastritis. Also, the transformation of FP to FIP was assessed by comparing specimens taken from the resected and residual parts of the stomach, respectively. Moreover, it appears that severe gastritis occurs in the gastric mucosa which shows a FIP. Therefore, we consider that the FIP indicates the position of the atrophic border.