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R J Vavrek

Publications and source records attributed to R J Vavrek.

At least 19 recordsLinked to original sources
PubMed2001

Metabolism-resistant bradykinin antagonists: development and applications.

Bradykinin plays many roles in normal and pathological physiology, but rapid enzymatic degradation made elucidation of its functions extremely difficult. Development of effective degradation-resistant antagonists made it possible to delineate these roles and to open the way for development of new drugs to control pathology due to excess production of bradykinin. Presently available peptide bradykinin antagonists are extremely potent, are completely resistant to enzymatic degradation, and are orally available. Non-peptide bradykinin antagonists have also been discovered. Development of bradykinin antagonists as drugs for cancer, inflammation and trauma is anticipated.

Animals↗
PubMed1993

Characterization of receptor-mediated actions of T-kinin.

T-Kinin (Ile-Ser-bradykinin) is unique to the rat. This study characterizes the receptors involved in T-kinin activity on both the intact isolated rat uterus and membrane receptor preparations of the rat uterus. The results show that T-kinin acts through kinin B2 receptors in the rat uterus as demonstrated by B2 receptor-antagonist inhibition. While the potency of T-kinin on rat uterus contraction was similar to that of bradykinin, binding studies showed that the affinity of T-kinin to the receptor was 10-fold lower than that of bradykinin. On the other hand, the D isomer of T-kinin, D-Ile-Ser-bradykinin, had an affinity for the receptor greater than that of T-kinin and was more potent in causing contraction. Comparing this finding with our previously published report that D-Ile-Ser-bradykinin is not active on the kinin receptor for vascular permeability indicates that the kinin receptors in the rat uterus are not the same as those previously reported in the smooth muscle of the vasculature, i.e. there exists subclasses of kinin B2 receptors. The data from binding studies on a variety of T-kinin analogues show that the substitution of hydroxyproline (Hyp) for Pro5, together with the D-configuration at Ile1 and/or Ser2 may be useful for the development of selective T-kinin antagonists. Studies involving pretreatment of the tissue with indomethacin demonstrated that prostaglandin release was more of a component of T-kinin's activity on the rat uterus than that of bradykinin.

Amino Acid Sequence↗
PubMed1992

Pseudopeptide analogs of bradykinin and bradykinin antagonists.

Over 100 reduced-bond analogs of bradykinin and bradykinin antagonists were designed, synthesized, and assayed in the classic smooth muscle and blood pressure assays in a further study of the structure-activity relationships of bradykinin. Both potent BK-like agonists and antagonists of BK activity were found among the reduced-bond analogs.

Amino Acid Sequence↗
PubMed1992

Bradykinin antagonists do not require a D-aromatic amino acid residue at position 7.

More than 200 new analogs of bradykinin have been synthesized and assayed. Analogs containing a D-aliphatic amino acid residue at position 7 and an L-aliphatic residue at position 8 are very potent antagonists of BK action on classical systems. Thus the "conventional wisdom" that a D-aromatic amino acid residue is required at sequence position 7 of BK antagonists must be modified.

Amino Acid Sequence↗
PubMed1992

Evaluation of cutaneous algogenic responses to bradykinin and inhibition by bradykinin analogs.

Bradykinin has long been postulated to have a major role in physiologic human pain production. We have developed a method to systematically quantify the algogenic response to bradykinin in human skin by the direct application of bradykinin to suction blister bases. After determination of the pain threshold to bradykinin, we examined the ability of synthetic peptide analogs of bradykinin to block bradykinin-induced pain. One of the six analogs (B4642) inhibited bradykinin-induced pain with at least one concentration in all subjects tested. This result could not be predicted on the basis of inhibition of bradykinin binding to its guinea-pig ileum receptor or to previous studies of bradykinin-induced pain production in animal models. This peptide may have an eventual role as a physiologic pain inhibitor.

Amino Acid Sequence↗
PubMed1992

Evidence for renal kinins as mediators of amino acid-induced hyperperfusion and hyperfiltration in the rat.

This study examined the role of tissue kallikrein and kinins in renal vasodilation produced by infusion of amino acids (AA). In rats fed a 9% protein diet for 2 wk, intravenous infusion of a 10% AA solution over 60-90 min reduced total renal vascular resistance and increased glomerular filtration rate (GFR) by 25-40% and renal plasma flow (RPF) by 23-30% from baseline. This was associated with a two- to threefold increase in urinary kinin excretion rate. Acute treatment of rats with aprotinin, a kallikrein inhibitor, resulted in deposition of immunoreactive aprotinin in kallikrein-containing connecting tubule cells and inhibited renal kallikrein activity by 90%. A protinin pretreatment abolished the rise in urinary kinins and prevented significant increases in GFR and RPF in response to AA. In a second group of rats pretreated with a B2 kinin receptor antagonist, [DArg Hyp3, Thi5,8 D Phe7]bradykinin, AA infusion raised urinary kinins identically as in untreated controls, but GFR and RPF responses were absent. Aprotinin or the kinin antagonist produced no consistent change in renal function in rats that were not infused with AA.AA-induced increases in kinins were not associated with an increase in renal kallikrein activity. Notably, tissue active kallikrein level fell 50% in AA-infused rats. These studies provide evidence that kinins generated in the kidney participate in mediating renal vasodilation during acute infusion of AA.

Amino Acids↗
PubMed1990

Bradykinin and its Gly6 analogue are substrates of cyclophilin: a fluorine-19 magnetization transfer study.

Fluorine-19 magnetization transfer experiments have been used to determine the rates of cis/trans isomerization about the X-Pro7 peptide bond in [p-fluoro-Phe8]bradykinin (cis/trans ratio approximately 0.1) and its Gly6 analogue (cis/trans ratio approximately 0.4). The measurements were carried out both prior to and after the addition of cyclophilin, which has recently been shown to have peptidyl-proline cis/trans isomerase activity and is the apparent target enzyme of the immunosuppressive agent cyclosporin A. Magnetization transfer measurements over the temperature range 40-75 degrees C in the absence of enzyme give activation energies of 22.8 and 23.0 kcal/mol for [p-fluoro-Phe8]bradykinin and its Gly6 analogue, respectively. The values for the uncatalyzed cis----trans rate constant, kc, are determined by extrapolation to be 4.8 x 10(-2) and 2.1 x 10(-2) s-1 for the two peptides at 25 degrees C. The enzyme-catalyzed enhancement of the cis/trans interconversion rate was proportional to added cyclophilin concentration and was strongly sequence specific, with bradykinin a much better substrate than [Gly6]bradykinin. At a peptide concentration of 2.2 mM, the catalytic activity expressed as kc per micromolar cyclophilin was determined to be 1.2 s-1/microM for [p-fluoro-Phe8]bradykinin and 0.13 s-1/microM for the Gly6 analogue. The increased cis----trans interconversion rates were strongly inhibited by cyclosporin A and the 6-(methylalanine) derivative, which bind to cyclophilin, but not by the 1-(tetrahydrofurfuryl) derivative of cyclosporin that binds weakly.

Amino Acid Isomerases↗
PubMed1990

Luminal responses to bradykinin on the isolated canine tracheal epithelium: effects of bradykinin antagonists.

We have tested the ability of several B2 antagonists on the responses of the open-circuited isolated canine tracheal epithelium to the luminal addition of Bradykinin (BK), Lys-BK, and substance P (SP). All three peptides produced biphasic changes in transmural potential difference (PD), an initial decrease (dip) followed by an increase (rise). The B2 antagonists D-Arg0 [Hyp3,Thi5,8,D-Phe7]BK (B5630) reversibly inhibited both the dips and the rise with IC50 values of 2.01 x 10(-8) and 1.54 x 10(-7) M, respectively. The responses to SP were unaffected even with high concentrations of the antagonist. Other antagonists tested [D-Phe1,7,Thi5,8]BK (B4158), [D-Phe2,7]BK (B4404), and [D-Phe7,Hyp8]BK (B5092) were ineffective.

Amino Acid Sequence↗
PubMed1990

Effects of kinins on cultured arterial smooth muscle.

The present study uses various kinin agonists and antagonists to examine the cellular mechanisms of bradykinin's actions on intracellular calcium, prostaglandins, and adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in cultured arterial smooth muscle cells (casmc) obtained from rat mesenteric arteries. Exposure to bradykinin produced a rapid release of calcium (peak less than or equal to 20 s) from intracellular stores and an increase in prostaglandin (PG) E2 and cAMP production in casmc. Compared with bradykinin, the bradykinin B1-agonist [des-Arg9]BK produced only a small increase in intracellular calcium. The bradykinin-mediated increase in intracellular calcium was competitively blocked by the B2 receptor antagonist [D-Arg-O-Hyp3-Thi5,8-D-Phe7]BK (B4307) but not the B1-antagonist ([des-Arg9-Leu8]BK). In addition, the similarity of the dose-response curves for the bradykinin-mediated increase in Ca2+, PGE2, and cAMP (half-maximal stimulation of 12, 11, and 13 nM, respectively) and the ability of the B2-antagonist (B4307) to block each of these effects of bradykinin suggest that all three effects are mediated by the same bradykinin (B2) receptor. Further studies revealed that increases in intracellular calcium are necessary for the bradykinin-mediated increase in PGE2 formation and the subsequent PGE2-dependent formation of cAMP. Taken together, these results suggest that bradykinin acts via a B2-receptor on arterial smooth muscle cells to release calcium from intracellular stores, leading to increases in PGE2 production and the PGE2-dependent activation of adenylate cyclase.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Effects of a kinin antagonist on renal function in rats.

We contrasted the effects of D-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-DPhe-Thi-Arg-TFA (kinin receptor antagonist), of aprotinin (kallikrein inhibitor), and of combined treatment with captopril (kininase II inhibitor) and phosphoramidon (neutral endopeptidase 24.11 inhibitor) on renal function of rats with and without 14-day deoxycorticosterone pretreatment (DOC, 25 mg.kg-1.wk-1 sc). Neither the kinin antagonist nor aprotinin affected renal function in rats with and without DOC pretreatment. Combined treatment with captopril and phosphoramidon caused in rats with and without DOC pretreatment augmentation (P less than 0.05) of kinin excretion (50-64%), glomerular filtration rate (12-11%), and sodium excretion (46-48%). In DOC-pretreated rats undergoing infusion of captopril and phosphoramidon, the superimposed administration of either the kinin antagonist or aprotinin caused the lowering of renal plasma flow, glomerular filtration rate, and sodium excretion. These effects of the kinin antagonist and aprotinin in rats infused with kininase inhibitors may be the consequence of blockade, respectively, of the renal actions and synthesis of kinins that, when in excess, elicit renal vasodilation and increase glomerular filtration rate and sodium excretion. Collectively, these observations suggest regulatory influence of kinins during conditions featuring increased renal kinin levels.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1990

Bradykinin contribution to renal blood flow effect of angiotensin converting enzyme inhibitor in the conscious sodium-restricted dog.

We examined the relative contribution of renin-angiotensin system blockade and bradykinin potentiation to the renal hemodynamic effect of the angiotensin converting enzyme inhibitor enalaprilat in sodium-deprived dogs. Six conscious dogs instrumented for monitoring of blood pressure (BP) and renal blood flow (RBF) were employed in five groups of experiments. In group 1, enalaprilat alone was administered, and it decreased BP by -24 +/- 3 mm Hg and increased RBF by 135 +/- 15 ml/min. During a constant intravenous infusion of saralasin (group 2), enalaprilat decreased BP by -7 +/- 3 mm Hg and increased RBF by 84 +/- 7 ml/min (delta BP and delta RBF, p less than 0.01 vs. group 1 by analysis of variance). During a constant intrarenal arterial infusion of saralasin (group 3), the respective changes in BP and RBF after enalaprilat were -10 +/- 3 mm Hg and 69 +/- 12 ml/min, and these results did not differ from those of group 2. The infusion of saralasin intravenously or intrarenal arterially decreased BP slightly and increased RBF. In the presence of an intravenous infusion of a specific bradykinin antagonist, D-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-D-Phe-Thi-Arg.TFA (B5630) (group 4), enalaprilat decreased BP by -28 +/- 4 mm Hg and increased RBF by 82 +/- 24 ml/min (delta RBF, p less than 0.01 vs. group 1).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1990

Kinin antagonists: design and activities.

Bradykinin antagonists effective in a great variety of kinin-responsive tissues have been developed and used to study the roles of kinins in various physiological and pathological phenomena. Structural changes required to yield antagonists and to confer high potency, tissue selectivity, and resistance to enzymatic degradation have been explored in several hundred analogs. Certain of these offer promise for the development of drugs effective against pain, inflammation, and asthma.

Animals↗
PubMed1989

A fluorometric study of the interaction of bradykinin with lipids.

The interaction of bradykinin (BK) with lipids has been followed by steady-state fluorescence measurements. Addition of either cerebroside sulfate (CS) or phosphatidylinositol (PI), solubilized with the nonionic surfactant C12E8, to BK or its analogue [Gly6]-BK enhances the relative fluorescence intensity of peptide emission at 288 nm. Fluorometric titration of the peptide with lipid has been used to quantitate the interactions in terms of stoichiometry and equilibrium constant. Job's method of continuous variation for the BK-CS interaction gave a stoichiometry of 1:2 for the complex. The value of the equilibrium constant, K, for the interaction of either BK or [Gly6]-BK with CS is 1.5.10(4) M-1. The BK-PI interaction is weaker; K = 5.0.10(3) M-1. Although electrostatic forces no doubt play a major role in these interactions, measurements on the model peptide Gly-Phe-Gly indicate that the phenylalanine residues of BK are disposed in the hydrophobic environment provided by the lipid-C12E8 mixed micelle. 13C-NMR measurements on [99% 13C alpha-Gly6]-BK show that there is no change in its cis/trans ratio upon interaction with CS. The increase in the relative fluorescence intensity of BK accompanying its cooperative interaction with sodium dodecyl sulfate (SDS) implicates the role of hydrophobic forces in this interaction as well. These results bear on the interpretation of the changes in circular dichroism (CD) of BK caused by SDS.

Amino Acid Sequence↗
PubMed1989

Induction of histamine release from human skin mast cells by bradykinin analogs.

Kinins are potent proinflammatory peptides that induce histamine release from rodent mast cells. We examined the ability of bradykinin, lysylbradykinin and a series of kinin analogs to cause histamine release from human basophils, human lung mast cells and human skin mast cells. At concentrations ranging from 0.1 microM to 1 mM, bradykinin failed to cause histamine release from any of the human histamine-containing cells studied. Lysylbradykinin was also without effect on basophils and lung mast cells, but was a weak secretagogue for human skin mast cells, inducing 5.5 +/- 3% (mean +/- SD) of total cellular histamine release at a concentration of 10(-5) M. Similarly, when sixteen recently developed bradykinin antagonists were examined, these compounds had no effect on basophils or lung mast cells but all sixteen induced dose-dependent histamine release from skin mast cells. The release process was temperature dependent and, at a concentration of 10(-5) M, the antagonists induced 8-27% histamine release. Although preincubation of cells with 10(-3) M bradykinin or des(Arg9) bradykinin significantly inhibited antagonist-induced histamine release, the requirement for such high concentrations of these peptides to cause inhibition suggested that histamine release is not mediated by either B1 or B2 kinin receptors. To understand further the mechanism of histamine release, we examined a series of bradykinin analogs with single amino acid substitutions in the bradykinin sequence. Replacement of proline7 in the bradykinin sequence with D-phenylalanine is the essential change used to convert kinin analogs into antagonists, and 10(-5) M [DPhe7]-bradykinin induced 8-10% histamine release. Other analogs, devoid of antagonist activity, however, such as [DPhe6]-bradykinin and [LPhe7]-bradykinin were able to induce equivalent levels of histamine release. The ability to induce histamine release appears to be related, at least in part, to aromaticity, since [DTrp6]-bradykinin and [DTrp7]-bradykinin induced greater amounts of histamine release than equivalent [DPhe]-analogs, causing approximately 20% histamine release at 10(-5) M. By contrast, [DAla7]-bradykinin was an ineffective stimulus. In summary, a single amino acid substitution can convert bradykinin into a secretagogue for human skin mast cells. The ability of kinin analogs to induce histamine release from skin mast cells, but not lung mast cells or basophils, emphasizes the heterogeneity of human histamine-containing cells.

Basophils↗
PubMed1989

Antagonism of the algesic action of bradykinin on the human blister base.

The effect of bradykinin (BK) and some analogues of BK on the human blister base was studied. BK produced reproducible dose-related increases in pain responses. A characteristic delay, which was not dose-related occurred between application of BK and the resultant response. The rank order of potency of several kinin analogues on the pain response was BK much much greater than sigma-cyclo-(Lys1-Gly6)-BK = sigma-cyclo-kallidin greater than des-Arg9-BK. No increase in pain response was seen with repeated application of the selective B1-receptor agonist des-Arg9-BK to the same blister base at 4h intervals. The B1 receptor antagonist des-Arg9-Leu8-BK was without effect against BK-induced responses. The B2-receptor antagonists, D-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-D-Phe-Thi-Arg-TFA and D-Pro-Phe-Arg-heptylamide produced significant antagonism of the bradykinin-induced pain responses at doses which had no effect against 5-hydroxytryptamine or potassium chloride. It is concluded that the kinin receptor mediating pain on the human blister base is of the B2 type.

Administration, Topical↗