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D Regoli

Publications and source records attributed to D Regoli.

At least 307 records · Page 17Linked to original sources
PubMed1982

Synthesis and biological activities of substance P antagonists.

Several substance P analogues containing various D-amino acid modifications have been synthesized by the solid-phase procedure, detached from the solid support by ammonolysis, and purified by gel filtration combined with reversed-phase chromatography. Three compounds were fair to very potent competitive antagonists of substance P on three bioassays, i.e., guinea pig ileum, rabbit mesenteric vein, and guinea pig trachea. [Arg6,D-Trp10]SP(6-11) is a reasonable antagonist in all three bioassays and [D-Pro4,D-Trp7,9]SP(4-11) is a very potent competitive antagonist with pA2 values ranging around 6.0.

Animals↗
PubMed1982

Structure-activity studies on the C-terminal amide of substance P.

Twelve C-terminal heptapeptide analogues of substance P have been synthesized by solid phase and by the classical solution method. The modifications concerned all the C-terminal primary amide of SP and should therefore help to understand the biological significance of this carboxamide, as evaluated by in vivo and in vitro bioassays. From the results it can be seen that not the slightest change of the two amide protons is tolerated without an important loss of activity: replacement of one or two amide protons with alkyl groups, extension of the amide to the hydrazide and its alkyl analogues, and exchange of the amide with an ester or a carboxylic acid all reduce the relative activity/affinity at least by 2-fold. It is not clear for what reason all these modifications produce such a drastic activity reduction.

Animals↗
PubMed1982

Preferred solution conformation of des-Arg9-bradykinin and analysis of structure-conformation-activity relationships in the series [Alan]des-Arg9-bradykinin.

This paper describes the solution conformation of the vasoactive peptide hormone des-Arg9-bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe). 1. By 1H-NMR spectroscopy we studied des-Arg9-bradykinin and its fragments bradykinin-(1-5), bradykinin-(1-6) in aqueous solution as a function of pH (titration) and in dimethylsulfoxide solution at two ionic states (cation and neutral ion species). 2. The preferred solution conformation which is most strongly stabilized in dimethylsulfoxide in the neutral ion species includes a distorted beta-turn II involving the N-terminal sequence of Pro2-Pro3-Gly4-Phe5 and most likely a C7-type bend in the C-terminal part Ser-Pro-Phe. 3. A complete series of analogous ([Alan]des Arg9-bradykinin, with n = 1, 2...8) was then investigated by circular dichroism and 1H-NMR spectroscopy in order to study the conformational role played by each residue and to delineate the local and the long-range effects on conformation brought about by the Xaa leads to Ala substitutions. Chosen spectral parameters (circular dichroic spectra, chemical shift variations and vicinal coupling constants) characteristic of the preferred solution conformation of the native sequence of des-Arg9-bradykinin are followed from analogue to analogue. The important conformational role of the arginine-1 side chain and its positive charge and the spatial proximity of the N-terminal and C-terminal groups, i.e. the folded structure of the peptide can be inferred from these data. 4. A comparison of the biological activities of the analogues with the conformative perturbations caused by the chemical alterations shows des-Arg9-bradykinin conformation and receptor affinity to be equally sensitive to single-residue substitutions. The correct orientation of the arginine-1 side chain, the precise geometry of the turn involving residues 2-5 and of the C-terminal Pro-Phe sequence are of primary importance.

Bradykinin↗
PubMed1982

Binding of [3H]des-Arg9-BK to rabbit anterior mesenteric vein.

Binding studies of [3H]des-Arg9-BK have been performed on pieces of rabbit anterior mesenteric veins. Kinetic studies have permitted us to evaluate an affinity constant of 1.04 X 10(-7) M, which is not so different from the apparent affinity constant determined by bioassay (1.6 X 10(-7) M). Furthermore, inhibition of the binding of [3H]des-Arg9-BK with various kinins results in an order of potency of kinins very similar to that observed in the bioassay. Taken together, these results suggest that we are dealing with binding sites which might be the same as those subserving the biological action of des-Arg9-BK (pharmacological receptors). The preincubation of tissues in Krebs' solution brings about an increase of the specific binding from 0.06 pmol/mg of wet weight at time 0 to 0.75 pmol after 24 h; cycloheximide inhibits this increase for at least 6 h. Veins taken from animals treated with LPS, which have shown an increase in sensitivity compared with veins extracted from untreated animals, have a higher number of specific binding sites for [3H]des-Arg9-BK. The results support the hypothesis that the increased response of tissues to des-Arg9-BK is due to the de novo synthesis of receptors for kinins in some experimental and pathological conditions.

Animals↗
PubMed1982

Effects of kinins on isolated blood vessels. Role of endothelium.

Bradykinin (BK) and des-Arg9-BK were used to determine whether the stimulatory and inhibitory actions of the kinins in various isolated vessels require the presence of endothelium and may be mediated by arachidonic acid metabolites. It was found that the presence of intact endothelium is required only for the relaxation of the dog common carotid artery in response to bradykinin. Stimulatory actions of both BK and des-Arg9-BK in arterial (rabbit aorta) and venous (rabbit jugular and mesenteric vein) smooth muscle do not require the presence of endothelium. Inhibition of the arachidonic acid cascade at various levels affects the relaxing action of acetylcholine (rabbit aorta and dog common carotid artery) while being inactive against both the relaxing (dog common carotid artery) and contractile actions (rabbit aorta, rabbit jugular and mesenteric veins) of bradykinin and des-Arg9-BK. Inhibitors of the arachidonic acid cascade also do not affect the inhibitory action of isopropylnoradrenaline on the rabbit aorta. The present results indicate that stimulant actions of kinins in isolated vascular smooth muscles do not require the presence of endothelium. Endothelium is required for the inhibitory actions of acetylcholine and bradykinin but not for that of isopropylnoradrenaline on the dog carotid artery. Moreover, the inhibition of arachidonic acid metabolism only affects the response of isolated vessels to acetylcholine. The present results suggest that several mechanisms may be involved in the inhibition of vascular tone by vasodilators.

Acetylcholine↗
PubMed1982

Pharmacological effects of peptides on tracheal smooth muscle.

Peptide and non-peptide agents were tested for their stimulatory or inhibitory effects on circular strips of guinea pig isolated tracheae. Substance P, eledoisin, physalaemin, neurotensin, angiotensin, histamine and carbachol were found to contract, while noradrenaline, dopamine, bradykinin, nucleotides (AMP, ADP, ATP) and prostaglandins (PGE1, PGE2, PGA2) induced concentration-dependent relaxations of tracheae contracted with substance P or carbachol. Indomethacin (2.8 X 10(-6) M) significantly potentiated the effect of substance P and blocked that of bradykinin. The contractions to substance P of tissues treated with indomethacin were not modified by atropine, methysergide, diphenhydramine, cimetidine, propranolol, phentolamine, [Leu8]-ATII, [Leu8]-des-Arg9-bradykinin, naloxone and baclofen. The order of potency of C-terminal fragments of substance P was: hexa(6-11) greater than hepta(5-11) greater than substance P greater than = octa(4-11). It is concluded that the guinea pig isolated trachea is a pharmacological preparation sensitive to numerous agents and useful for studying structure-activity relationship and the mechanism of cellular action of several peptides, particularly substance P.

Animals↗
PubMed1982

Effects of peptides and amines on isolated guinea pig tracheae as influenced by inhibitors of the metabolism of arachidonic acid.

Stimulants (histamine, acetylcholine and substance P) and relaxants (isoprenaline and bradykinin) of the guinea pig trachea were tested in the absence and presence of mepacrine, eicosatetraynoic acid, BW 755C and indomethacin in order to evaluate the involvement of prostaglandins and congeners in the effects of amines and peptides. While histamine appeared to stimulate tracheal smooth muscle directly, acetylcholine acted in part by promoting the release of contractile leukotrienes. Substance P was unable to express its full stimulating effect because of a likely release of an inhibitory prostaglandin. Isoprenaline inhibited tracheal smooth muscles by a direct action, while the relaxation of the trachea in response to bradykinin appeared to depend on the release of prostaglandins, since it was reduced in the presence of inhibitors of cyclo- and lipooxygenase. It is concluded that enzymes involved in the metabolism of arachidonic acid are present in the guinea pig trachea and are activated both by relaxant and stimulant agents.

Amines↗
PubMed1981

The hypotensive effect of centrally administered neurotensin in rats.

We have evaluated the cardiovascular effects of intracerebroventricular (i.c.v.) injections of neurotensin (NT) in pentobarbital-anesthetized rats. In most animals, the i.c.v. injection of NT (5.4, 10.8 and 16.2 nmol/rat) induced a dose-dependent fall of the arterial blood pressure. This effect was usually rapid in onset (30-60 sec) and of short duration (approximately 1-4 min). It was not preceded nor accompanied by any significant alteration of the heart rate. In about 25% of the animals, the vasodepressor effect of i.c.v. injections of NT was long lasting (30-45 min). Conscious rats were much less sensitive than anesthetized animals. The hypotensive effects of intravenously (i.v.) administered NT was fully maintained in animals made tolerant to the hypotensive effect of centrally administered NT. Similarly, the animals made unresponsive to i.v. injections of NT either by repeated i.v. injections of NT (e.g. tachyphylaxis) or by a chronic treatment with compound 48/80, still responded normally to centrally administered NT. The results suggest the existence of at least two anatomically distinct sites of action through which NT can induce hypotension in rats. One appears to be located in the periphery and the other, in the central nervous system.

Animals↗
PubMed1981

Receptors for bradykinin in murine peritoneal macrophages: modulation of short-term spreading.

The order of potency of bradykinin (bk) and four analogues, with respect to their modulation of peritoneal macrophage short-term spreading, suggests the presence of two peptide receptors in these cells which are responsible for antagonistic effects. Spreading inhibition and stimulation are mediated by the B1- and B2-types respectively. The implications of these results are highlighted in view of the hypothesis that the anti-inflammatory compound of the 1500--1000 molecular weight peptide fraction purified from malignant cell culture supernatants could be a kinin metabolite and a feedback mediator of inflammatory reactions.

Animals↗
PubMed1981

Synthesis of peptides by the solid-phase method. 6. Neurotensin, fragments, and analogues.

Neurotensin (NT) and 24 related compounds, including fragments or analogues modified at the C-terminal end of the parent molecule, have been prepared by the solid-phase method. After purification by cation-exchange chromatography, the compounds were characterized by thin-layer chromatography, amino acid analysis, elemental analysis, and high-pressure liquid chromatography. The stimulating effects of the peptides were evaluated in rat stomach strips, in isolated spontaneously beating atria of guinea pigs, and in the coronaries of perfused rat hearts. The differences between the biological activities of these compounds are discussed.

Animals↗
PubMed1981

Biological activities of photoaffinity labeling analogues of kinins and their irreversible effects on kinin receptors.

Several analogues of bradykinin and [des-Arg9]bradykinin with potentially reactive groups have been tested for their biological activities. In these analogues, phenylalanine was replaced by the aromatic amino acid (4'-nitro)Phe, (4'-amino)Phe, (4'-azido)Phe, and (4'-diazonium)Phe, as well as with other residues. [Des-Arg9]bradykinin and the octapeptide analogues were tested on rabbit aorta strips, an assay organ containing the B1 receptor which is activated by the octapeptide [des-Arg9]bradykinin. Strips of rabbit jugular vein served as bioassays for bradykinin and the nonapeptide analogues, because the rabbit jugular vein bears the receptor B2 which is sensitive to bradykinin nonapeptides. The biological findings support the interpretation that kinins act on two different receptor types, since the potency orders of the analogues in the two bioassays are different. All potential photolabels retained reasonable affinities in the dark, except [(4'-azido)Phe8,des-Arg9]bradykinin, which, however, proved to be a weak and competitive antagonist of [des-Arg9]bradykinin on the rabbit aorta. Inactivation experiments with the unstable (4'-diazonium)Phe-containing peptides did not show any irreversible effect in the two bioassays. Photoaffinity labeling experiments with the azido and the nitro peptides gave irreversible and specific effects on both the rabbit aorta and the jugular vein. [(4'-Azido)Phe8,des-Arg9]bradykinin photolyzed at 365 nm on the rabbit aorta reduced the sensitivity of this tissue against [des-Arg9]bradykinin specifically to about one-third of its initial value. [(4'-Azido)Phe5]bradykinin reduced the sensitivity of the rabbit jugular vein to bradykinin by more than 50%. The observed irreversible effects were always loss of myotropic activity and never permanent contraction.

Affinity Labels↗
PubMed1981

Pharmacological studies of kinins in venous smooth muscles.

The myotropic effects of bradykinin (BK) and other kinins in two isolated veins, the rabbit jugular and the guinea pig anterior mesenteric, have been studied. The effects of degradation on the biological activities of these compounds and the receptor types mediating their myotropic effects have been determined. It has been found that contractions elicited by kinins in these veins result from direct actions on specific receptors. Both veins contain active kininase II (but not active carboxypeptidases A or B) which interferes with the measurement of the myotropic effects and can be blocked by 1-(D-3-mercapto-2-methyl-3-oxopropyl)-L-proline (SQ 14225). The slopes but not the maxima of the concentration-response curves of BK and other kinins measured in the presence of SQ 14225 are different from those recorded in its absence whereas no significant changes are observed in concentration-response curves obtained with the analogue [D-Phe8]-BK, which resists degradation by kininase II. BK is more potent than its fragment sequence des-Arg9-BK and the effects of kinins are antagonized by dihydrochlorprothixene and beta-phenylalanine hexyl ester. These findings suggest that the rabbit jugular and the guinea pig anterior mesenteric veins contain receptors of the B2 type. The findings presented in this paper indicate that the rabbit jugular vein and the guinea pig anterior mesenteric vein are sensitive preparations for kinins and they can be useful for structure-activity studies of these peptides. A correct evaluation of the relative affinities of various kinins is, however, only possible by eliminating the interference of kininase II.

3-Mercaptopropionic Acid↗
PubMed1981

Structure-activity study of kinins in vascular smooth muscles.

To explore further relations between the chemical structure and the biological activities of kinins, a series of bradykinin fragments and analogues was prepared by the solid-phase method. Bradykinin and kallidin were also extended at the C- or the N-terminal end by the addition of one or more residues in order to evaluate the importance of peptide chain length and of additional positive charges at the N-terminal end for the biological activity. After purification by cation-exchange chromatography and gel filtration, the compounds were characterized by thin-layer chromatography, paper electrophoresis, elemental analyses, and amino acid analyses. All compounds were tested on three vascular preparations (the dog common carotid artery, the rabbit jugular vein, and the guinea pig anterior mesenteric vein) in order to measure their relative potencies as relaxant (on the dog common carotid artery) or as stimulant (the two veins) of vascular smooth muscles. The compounds were also tested on the cat terminal ileum and the rabbit aorta for comparison. The results reported in this paper indicate that all new analogues of bradykinin as well as some fragments and analogues described before by us and by other workers are full agonists in the three vascular preparations. No partial agonists or antagonists have been identified. The order of potency of the various kinin analogues is similar in the three vascular preparations and follows the same pattern as that found in the cat terminal ileum. It is therefore concluded that (a) the three vascular preparations utilized in the present experiment possess a B2 receptor type that appears to be similar to that of the cat terminal ileum and of the rat uterus described before and (b) receptors of the B2 type are able to mediate both the inhibitory and the excitatory actions of kinins in vascular smooth muscles.

Animals↗