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D Regoli

Publications and source records attributed to D Regoli.

At least 199 records · Page 11Linked to original sources
PubMed1991

Structure-activity studies of bradykinin and related peptides. B2-receptor antagonists.

Thirty-seven compounds were tested as antagonists of kinin B2- and B1-receptors to identify the chemical changes required to obtain antagonism, improve antagonist affinity, and eliminate residual agonistic activities. Apparent affinity of antagonists was evaluated in terms of pA2 on the rabbit jugular vein, the dog carotid and renal arteries, the hamster urinary bladder, the guinea pig ileum, the rat vas deferens, the guinea pig trachea, and the rabbit aorta, using bradykinin and desArg9-bradykinin as B2- and B1-receptor activators. Replacement of Pro7 of bradykinin with D-Phe leads to antagonism; substitution of Pro3 by Hyp and extension of the peptide chain at the N-terminal with a D-Arg residue improves the affinity of antagonists; acetylation of N-terminal amine function reduces residual agonistic activity; these changes, combined with the replacement of Phe8 by Leu as in Ac-D-Arg[Hyp3,D-Phe7,Leu8]-bradykinin, led to potent full B2-receptor antagonists. Affinity of antagonists differs markedly between highly sensitive (rabbit jugular vein, dog carotid and renal artery), moderately sensitive (hamster urinary bladder, guinea pig ileum, and rat vas deferens), and insensitive preparations (the guinea pig trachea) in which antagonists act as potent stimulants. High concentrations of antagonists block bradykinin completely in the rabbit jugular vein but not in the guinea pig ileum, suggesting that kinins stimulate the moderately sensitive tissues by two mechanisms, of which only one is blocked by antagonists. It thus appears that kinins act on various B2-receptor subtypes or by different action mechanisms.

Animals↗
PubMed1991

DuP 753 is a specific antagonist for the angiotensin receptor.

2-n-Butyl-4-chloro-5-hydroxy-methyl-1-[(2'-(1H)-tetrazol-5-yl)biph enyl-4- yl)methyl]imidazol potassium salt (DuP 753) is a nonpeptide angiotensin II receptor antagonist that inhibits the contractile effects of angiotensin II competitively and shows pA2 values of 8.27 on the rabbit aorta and jugular vein, 8.66 on the rat portal vein and stomach, 8.19 on the rat urinary bladder, and 8.36 on human colon, ileum, and urinary bladder. This agent (more than 10(-5) M) exhibits no agonistic activity and does not affect the contractile effects of norepinephrine, acetylcholine, bradykinin, desArg9-bradykinin, substance P, neurokinin A, neurokinin B, or bombesin in the various tissues. The present results demonstrate that DuP 753 is a potent nonpeptide antagonist with high affinity, specificity, and selectivity for the angiotensin receptor.

Adrenergic alpha-Antagonists↗
PubMed1990

Antagonists for the neurokinin NK-3 receptor evaluated in selective receptor systems.

Four isolated vessels that are monoreceptor systems for neurokinins, the dog carotid artery and rabbit jugular vein (NK-1), the rabbit pulmonary artery (NK-2) and the rat portal vein (NK-3), were used to compare the activities of selective neurokinin agonists and evaluate the affinities of new NK-3 antagonists. Chemical modifications in the partial sequences NKA (4-10) and NKB (4-10), particularly the replacement of Val7 with an aromatic residue (Tyr, MePhe or Trp) and the extension of the peptide backbone in position 8, obtained with beta-Ala, led to compounds that maintain weak agonistic activities on the NK-1 and NK-2, and some of them also on NK-3 receptors but exert potent antagonism against NKB on the NK-3 receptor of the rat portal vein. Antagonistic affinity is the highest when Trp is used in position 7 of [beta-Ala8]-NKA (4-10) and MePhe in position 7 of [beta-Ala8]-NKB (4-10). Antagonism is selective for NKB or [MePhe7]-NKB, and appears to be specific, since the most active compound [Trp7, beta-Ala8]-NKA (4-10) is inactive against bradykinin on the rabbit jugular vein (B2 receptor), against SP on the rabbit jugular vein (NK-1 receptor), against desArg9-bradykinin on the rabbit aorta (B1 receptor), and against angiotensin II and histamine (AT and H receptors, respectively) in the rabbit aorta. The new NK-3 receptor antagonists described in the present study provide useful tools for neurokinin receptor characterization and for determining the roles of neurokinins in physiopathology.

Animals↗
PubMed1990

Characterization of a B2-bradykinin receptor in rat renal mesangial cells.

The specific binding of bradykinin (BK) was investigated using membrane fractions from mesangial cells in primary culture, a cloned cell line, and in intact adherent cells with three different radiolabelled BK analogues: 125I-[Tyr0]BK, 125I-[Tyr5]BK and 125I-[Tyr8]BK. The best radioligand was 125I-[Tyr0]BK, and assay conditions were determined to ensure maximal stable binding. Binding appeared to be reversible and not to be inhibited by a wide variety of protease inhibitors including converting enzyme inhibitor and phosphoramidon. The maximum density of binding sites (Bmax) was about 88 +/- 18 fmol/mg protein, which is equivalent to about 6000 sites/cell, and the dissociation constant averaged 2 nM. No significant difference in Bmax was observed between membranes from cells in primary culture and those from cloned cells. Of the BK analogues tested, unmodified BK exhibited the highest inhibition constant (close to 10(-10) M). No displacement of 125I-[Tyr0]BK was observed in the presence of the B1 agonist des-Arg9-BK or several unrelated peptides, including atrial natriuretic factor and angiotensin I and II, whereas 50% inhibition of binding was achieved with the B2 antagonist [D-Arg,Hyp3,D-Phe7]BK (10(-9)M). Addition of BK for 3 min to the incubation medium of cloned mesangial cells induced a dose- and time-dependent increase in PGE2 unlike des-Arg9-BK, which showed no such effect. The secretion was strongly inhibited by prior incubation with the B2 antagonist [D-Arg,Hyp3,D-Phe7]BK. The pharmacological profile of the binding site determined with various BK agonists and antagonists, and the stimulating effect of binding site activation on prostaglandin release strongly suggest that B2-kinin-like receptors are present in rat mesangial cells.

Animals↗
PubMed1990

125I-BH[Sar9, Met(O2)11]-SP, a new selective ligand for the NK-1 receptor in the central nervous system.

The selective agonist [Sar9,Met(O2)11]-SP was radioiodinated with 125I-Bolton Hunter in order to study its binding to rat brain membranes and for further comparison with 125I-BH.SP. Specific binding of 125I-BH[Sar9,Met(O2)11]-SP was temperature-dependent, saturable and reversible. In brain homogenates, 125I-BH[Sar9,Met(O2)11]-SP interacted with a single class of high affinity (kd = 1.0 nM) non-interacting binding sites (Bmax of 15 fmol/mg protein). In the central nervous system, 125I-BH-[Sar9,Met(O2)11]-SP apparently labeled the same number of binding sites as 125I-BH.SP (19 fmol/mg proteins). Competition studies with tachykinins, neurokinins and selective neurokinin agonists indicated that the pharmacological profile of the site labeled by 125I-BH[Sar9,Met(O2)11]-SP is identical with that of NK-1 receptors. In dose-displacement studies made with radiolabeled SP and [Sar9,Met(O2)11)]-SP, an excellent correlation (r = 0.96) was found for the Ki values of the different compounds tested; these findings suggest that both radioligands recognize the same receptor in rat brain. The affinity (Ki) of various neurokinin-related peptides for the brain site were compared with their biological activities on various isolated organs (dog carotid artery, guinea-pig ileum, rat portal vein). NK-1 binding sites characterized in rat brain homogenates appear to be identical with those present on the dog carotid artery, a preparation known to possess exclusively the NK-1 receptor type.

Animals↗
PubMed1990

Binding characteristics of [125I]Bolton-Hunter [Sar9,Met(O2)11]substance P, a new selective radioligand for the NK1 receptor.

The selective tachykinin agonist [Sar9,Met(O2)11]substance P (Sar-SP) was radioiodinated with [125I]Bolton-Hunter reagent and the product [125I]Bolton-Hunter-[Sar9,Met(O)2)11]SP (BHSar-SP) purified using reverse phase HPLC. Autoradiographic studies showed dense specific binding of BHSar-SP over the rat submandibular gland and over several regions in rat brain, with very low nonspecific binding, identical with the pattern of binding sites seen in a parallel study with [125I]Bolton-Hunter SP (BHSP). In homogenate binding experiments, BHSar-SP bound with high affinity to a single site in membranes from rat brain (KD 261 pM) and rat submandibular gland (KD 105 pM). Comparative values for BHSP were 495 and 456 pM, i.e. of two and four fold lower affinity than BHSar-SP. Association of BHSar-SP to membranes from brain (k+1 3.7 x 10(9) M-1 min-1) was faster than to membranes from salivary gland (k+1 5.6 x 10(8) M-1 min-1). In competition studies, BHSar-SP was displaced from salivary gland membranes by substance P (SP) approximately physalaemin greater than or equal to Sar-SP approximately SP-(3-11) greater than SP-(5-11) much greater than neurokinin A (NKA) approximately eledoisin = kassinin = SP-methyl ester greater than or equal to neurokinin B (NKB) much greater than [Nle10]NKA-(4-10) greater than [MePhe7]NKB-(4-10). In brain membranes, the rank potency order was SP greater than Sar-SP greater than or equal to physalaemin greater than SP-(3-11) greater than SP-(5-11) greater than NKA greater than or equal to eledoisin much greater than NKB greater than kassinin greater than SP-methyl ester: however [MePhe7]NKB-(4-10) and [Nle10]NKA-(4-10) were ineffective competitors at concentrations up to 1 microM. Both binding patterns are consistent with BHSar-SP binding to an NK1 site. With the exception of SP, Sar-SP, SP-(3-11) and physalaemin, all competitors were 5 to 54 times less potent at BHSar-SP binding sites in brain than in salivary gland. These data reveal some differences in characteristics of NK1 binding sites in brain and submandibular gland. Although of higher affinity, BHSar-SP does not appear greatly more selective than BHSP in its ability to define NK1 binding sites.

Amino Acid Sequence↗
PubMed1990

The rabbit jugular vein is a contractile NK-1 receptor system.

Rabbit isolated jugular veins respond to substance P and related neurokinins with concentration-dependent contractions which appears to be due to the activation of a single neurokinin receptor of the NK-1 type. This is demonstrated by the order of potency of neurokinins and some of their fragments as well as by the strong activity of NK-1-selective agonists and the weakness of NK-2- and NK-3-selective agonists. The present results indicate that the rabbit jugular vein provides a sensitive, specific and selective NK-1 preparation which responds directly to neurokinins with contractions and therefore can be useful for characterization of NK-1 agonists and antagonists.

Angiotensin II↗
PubMed1990

Biological activity of N-terminal fragments of calcitonin gene-related peptide.

The i.v. injection of human alpha-calcitonin gene-related peptide (CGRP) in urethane-anesthetized rats produced hypotension and tachycardia. The N-terminal fragments, CGRP-(1-12), CGRP-(1-15) and CGRP-(1-22) displayed biological activity, although with less potency than the natural peptide. These findings provide the first evidence for biological agonist activity of N-terminal CGRP fragments.

Animals↗
PubMed1990

Receptors for neurokinins in human bronchus and urinary bladder are of the NK-2 type.

Human tissues such as the isolated bronchus and urinary bladder respond to neurokinins with concentration-dependent contractions, which appear to be due to the activation of receptors. We characterized these receptors in the present study using agonists (the naturally occurring neurokinins and some selective agonists) as well as newly identified antagonists. The order of potency of the agonists in the two preparations was as follows: neurokinin A (NKA) greater than substance P (SP) greater than neurokinin B (NKB) (bronchus) and NKA greater than NKB greater than SP (bladder), which suggests the presence of NK-2 receptors. This was confirmed by data obtained with two antagonists, one of which was shown to be competitive and selective for NK-2 type receptors. It thus appears that receptors of the NK-2 type are present in humans along the tracheo-bronchial tree and in the urinary system.

Bronchi↗
PubMed1990

A highly selective NK-2 tachykinin receptor antagonist containing D-tryptophan.

The classical approach used in the development of substance P (SP) antagonists, i.e. the introduction of multiple D-tryptophan (D-Trp), was successfully extended to neurokinin A (NKA). Thus, a new NK-2-selective tachykinin receptor antagonist, namely [Tyr5, D-Trp6,8,9, Arg10]NKA-(4-10), was developed that had pA2 values of 5.2, 7.9 and 4.9 in three monoreceptor in vitro assays for NK-1, NK-2 and NK-3 tachykinin receptors, respectively.

Amino Acid Sequence↗
PubMed1990

New selective bradykinin receptor antagonists and bradykinin B2 receptor characterization.

Substantial progress has been made recently in the field of kinin pharmacology with the identification of sensitive bioassay organs and the discovery of bradykinin B2 receptor antagonists. Data obtained with such compounds in various laboratories support the hypothesis that kinins act on multiple (at least two) receptor types. Domenico Regoli and colleagues review here the basic criteria of receptor characterization as they apply to kinins and present a critical analysis of the bioassay organs and B2 receptor antagonists currently used in kinin pharmacology.

Animals↗
PubMed1990

5,5-Dimethylthiazolidine-4-carboxylic acid (DTC) as a proline analog with restricted conformation.

Spectroscopic evidence is presented for the lack of intramolecular hydrogen bonding in a simple peptide derivative of 5,5-dimethylthiazolidine-4-carboxylic acid (Dtc). The infrared spectrum of Boc-Pro-Ile-OMe 1 in nonpolar solvents displays two N-H stretching bands at 3419 and 3330 cm-1 in CCl4 and one at 3417 and 3328 cm-1 in CHCl3. The low frequency band at 3328-3330 cm-1 may be assigned to conformations with an intramolecular hydrogen bond between the Ile N-H and Boc C = O. The band at 3417-3419 cm-1 is the normal Ile N-H stretch. In the polar solvent CH3CN only one NH stretching band at 3365 cm-1 is observed. The IR spectrum of Boc-Dtc-Ile-OMe 2, on the other hand, displays one N-H stretching band at 3423 cm-1 in CCl4 and one at 3418 cm-1 in CHCl3. The IR spectrum of 2 does not display the N-H stretching band that would arise from intramolecular hydrogen bonding between the Boc C = O and Ile N-H. The lack of intramolecular hydrogen bonding for Boc-Dtc-Ile-OMe 2 was evident also in the NMR spectra in nonpolar solvents. The 1H-NMR spectrum of the Pro dipeptide 1 in 50% CDCl3/C6D6 at 20 degrees displayed two Ile-NH signals at 6.58 and 7.74 ppm. The latter signal corresponds to the intramolecularly hydrogen bonded Ile-NH in the trans-Boc isomer of 1 (60% of the total population), while the former signal corresponds to the nonhydrogen bonded Ile-NH in the cis-Boc isomer.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

Structure-activity studies on bradykinin and related peptides: agonists.

1. Bradykinin, kallidin, T-kinin, [Hyp3]-bradykinin and several analogues were prepared by solid-phase synthesis and purified by high performance liquid chromatography. 2. The various peptides were tested for their abilities to relax the dog carotid and renal arteries, or to contract the rabbit jugular vein and aorta, in order to measure their activities on BK2 (the first three preparations) or BK1 (the rabbit aorta) receptors. The dog renal artery without endothelium was also used as a BK1 receptor system. 3. T-kinin was found to be less active than bradykinin, while the replacement of Pro3 with Hyp favoured BK2 receptor occupation. [Hyp3,Tyr(Me)8]-BK was found to be a selective BK2 receptor agonist. 4. Amidation or methylation of the C-terminal carboxyl decreased activity, while extension of the N-terminal with Sar or D-Arg increased affinity and selectivity for BK1 (Sar) and affinity for BK2 (D-Arg) receptors. Acetylation of N-terminal amide brought affinity down to 10% or less. 5. Replacement of the peptide bonds Phe8-Arg9 to protect from kininase I and II, decreased affinities slightly, but was incompatible with additional changes at the N-terminal or in the peptide bond Gly4-Phe5. 6. Substitution of C-terminal Phe in desArg9-BK (the BK1 receptor stimulant) with D-Phe increased potency and selectivity for BK1 receptors while protecting from carboxypeptidases. Sar[D-Phe8]desArg9-BK was found to be a potent and selective BK1 receptor agonist.

Animals↗
PubMed1990

Competitive antagonists discriminate between NK2 tachykinin receptor subtypes.

1. We have compared the ability of various tachykinins and selective tachykinin receptor agonists to induce contraction of the endothelium-denuded rabbit pulmonary artery (RPA) and hamster trachea (HT) and have estimated the affinity of some newly developed NK2 selective antagonists in the same tissues. 2. In confirmation of previous findings, experiments with the agonists indicated that NK2 receptors are the main if not the sole mediators of the response to tachykinins in both RPA and HT. No evidence for significant degradation of neurokinin A (NKA) was found in either tissue when experiments were repeated in the presence of a mixture of peptidase inhibitors (thiorphan, captopril and bestatin, 1 microM each). 3. The peptide antagonists tested were: Peptide I = [Tyr5, D-Trp6,8,9, Arg10]-NKA(4-10); Peptide II = [Tyr5, D-Trp6,8,9, Arg10]-NKA(3-10); Peptide III = Ac-Leu-Asp-Gln-Trp-Phe-Gly-NH2. The three peptides produced a concentration-dependent rightward shift of the concentration-response curve to NKA in both RPA and HT with no significant depression of the maximal response attainable. The slopes of the Schild plots were not significantly different from unity, indicating a competitive antagonism. Peptides I and II were about 100 times more potent in the RPA than in the HT, while Peptide III was about 100 times more potent in the HT than RPA. 4. The pA2 values obtained in these two tissues with the three antagonists were not significantly different when tested in the absence or presence of peptidase inhibitors, or when a selective NK2 receptor agonist, [beta Ala8]-NKA(4-10) was used instead of NKA. Similar pA2 values were obtained after 15 or 90min of incubation with the antagonists. Peptides I, II and III had no inhibitory effect on contractions produced by noradrenaline in the RPA or by carbachol in the HT. 5. Peptides I, II and III showed weak or no antagonistic activity toward the vasodilatator effect of substance P in the dog carotid artery (NK, receptor-mediated) or toward the contractile effect of neurokinin B in the rat portal vein (NK3 receptor-mediated). 6. These results provide pharmacological evidence for heterogeneity of NK2 receptors in the RPA and HT. The NK2 receptors present in these tissues are not discriminated by natural tachykinins or selective agonists, but are recognized with very different affinity by NK2 receptor antagonists.

Amino Acid Sequence↗
PubMed1990

Inhibitors of peptidases: how they influence the biological activities of substance P, neurokinins, kinins and angiotensins in isolated vessels.

Myotropic effects of various peptides were measured in three isolated vessels, the dog carotid artery, the rabbit pulmonary artery and the rat portal vein in the absence and in presence of several peptidase inhibitors, in order to evaluate the interference by metabolism with the peptides' biological activities. After adequate controls, captopril (4.6 x 10(-6) mol/l), thiorphan (1.0 x 10(-6) mol/l), phosphoramidon (4.6 x 10(-6) mol/l), chymostatin (1 mg/l), bestatin (8.1 x 10(-6) mol/l) or bacitracin (1.4 x 10(-5) mol/l) were left in contact with the tissues for 20-40 min to inhibit tissue peptidases before measuring again the biological effects of the various peptides. In some experiments, mergetpa (5.4 x 10(-6) mol/l) was used. All peptidase inhibitors were inactive on their own and only captopril potentiated the effects of substance P, neurokinins, bradykinin and inhibited angiotensin I in two preparations, the dog carotid artery, the rat portal vein, and, excluding bradykinin, also in the rabbit pulmonary artery. Captopril and thiorphan significantly potentiated the maximal response of the rat portal vein to substance P and mergetpa inhibited completely the effect of bradykinin on the rabbit pulmonary artery. The present findings suggest that the most active proteolytic enzyme interfering with the biological effects of vasoactive peptides on three isolated vessels is the angiotensin-converting enzyme (kininase II).

Angiotensin II↗
PubMed1990

Inhibitors of peptidases: how they influence the biological activities of substance P, neurokinins, bradykinin and angiotensin in guinea pig, hamster and rat urinary bladders.

Neurokinins, bradykinin and angiotensins were tested in isolated urinary bladder of the guinea pig, the hamster and the rat, in the absence and in presence of a variety of peptidase inhibitors in order to establish if peptide degradation interferes with the bladder contractions elicited by the three types of peptides. Indeed, the effects of neurokinins, bradykinin and angiotensin I in the guinea pig bladder were significantly enhanced by captopril (4.6 x 10(-6) mol/l), chymostatin (1 mg/l), phosphoramidon (4.6 x 10(-6) mol/l) and thiorphan (1.0 x 10(-6) mol/l), while only captopril was found to potentiate the effects of the same peptides in the rat bladder. The four peptidase inhibitors, as well as bacitracin were found to modify the responses of the hamster urinary bladder to one or another or to all three groups of peptides and to DiMeC7. The present results suggest that the urinary bladders of various species have different types of active proteolytic enzymes: only the angiotensin-converting enzyme appears to be present in the rat bladder, while the same enzyme and possibly two additional endopeptidases interfere with the myotropic effects of neurokinins, kinins and angiotensins in the guinea pig and the hamster bladder.

Angiotensin II↗
PubMed1990

Structure-activity study of neurokinins: antagonists for the neurokinin-2 receptor.

A series of 21 peptides were synthesized and tested in a variety of isolated organs in order to determine their potential as neurokinin-2 (NK-2) antagonists. The peptides have been tested in the three monoreceptor systems, the dog carotid artery (NK-1), the rabbit pulmonary artery (NK-2) and the rat portal vein (NK-3) as well as on other preparations containing NK-2 receptors, such as the rat vas deferens, the hamster urinary bladder, the guinea-pig trachea and the human urinary bladder. Some of the compounds have also been tested on the human isolated bronchus. Three compounds, of which two are linear peptides, Ac.Leu-Asp-Gln-Trp-Phe-Gly.NH2, Thr-Asp-Tyr-D-Trp-Val-D-Trp-D-Trp-Arg.NH2 and a cyclic one, cyclo[Gln-Trp-Phe-Gly-Leu-Met] have been shown to reduce or eliminate the effects of neurokinin A (NKA) in practically all the preparations containing NK-2 receptors. The first compound was found to be selective for the NK-2 receptor and showed only agonistic or no activity on the other receptor systems, while the second compound showed some antagonistic effects not only on the NK-2 but also on the other systems. The cyclic compound was found to be fairly selective for the NK-2 receptor. The first compound (Ac.Leu-Asp-Gln-Trp-Phe-Gly.NH2) was characterized with respect to its specificity for neurokinins (NK): it was found to be inactive on receptors for acetylcholine, noradrenaline, angiotensin and des Arg9-bradykinin in the rabbit pulmonary artery. Moreover, the compound exerted a competitive type of antagonism on the rabbit pulmonary artery and on the hamster urinary bladder. Although of moderate affinity, the NK-2 receptor antagonists described in this paper provide important tools for pharmacological studies on NK.

Amino Acid Sequence↗