Degradation Kinetics of Leucine5-Enkephalin by Plasma Samples from Healthy Controls and Various Patient Populations

Mosnaim, Aron D.; Wolf, Marion E.; Nguyen, Tao D.; Puente, Javier; Freitag, Frederick G.; Diamond, Seymour

doi:10.1097/00045391-200007030-00006

Cited by 18 publications

(37 citation statements)

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“…Fractions from two such samples were used to examine the result of thaw and freeze (up to four times over a period of 12 months) on the effect of representative drugs (thioridazine and fluphenazine) on the rate of LEU metabolism. Aliquots of plasma samples have been used in different protocols [13].…”

Section: Methodsmentioning

confidence: 99%

“…due redissolved in buffer (200 Ìl) and after counting an aliquot, unchanged LEU and labeled LEU metabolites (if any) were identified (TLC) and individually quantitated [12,13]. Chemical tested included various clinically used antipsychotic drugs representing significantly different chemical structures e.g., chlorpromazine, fluphenazine, prochlorperazine, thioridazine, trifluoperazine, haloperidol, sulpiride, thiothixene, loxapine, clozapine and molindone.…”

Section: Methodsmentioning

confidence: 99%

“…1), and MET; H-Tyr-Gly-Gly-PheMe-OH, YGGFM, respectively] are involved in the regulation of various physiological and behavioral processes, and appear to play a role in the pathophysiology of various diseases [1][2][3][4][5][6][7][8][9][10]. Whereas little is known regarding the in vivo kinetics of LEU metabolism in humans, in vitro studies show that incubation of this peptide with plasma results in its rapid and complete degradation, mostly as a result of tyrosine-glycine amide bond hydrolysis [11,12,13]. Consistently, and irrespective of gender, age, race, length of frozen plasma storage time, or repeated sample freezing and thawing, over 95% of the initially added [ 3 H]-tyrosine LEU is recovered as the free labeled-aminoacid (after 30 min reaction; pH 7.4 and 37°C), with little formation of any of the other possible LEU degradation fragments [13].…”

Section: Introductionmentioning

confidence: 99%

“…Whereas little is known regarding the in vivo kinetics of LEU metabolism in humans, in vitro studies show that incubation of this peptide with plasma results in its rapid and complete degradation, mostly as a result of tyrosine-glycine amide bond hydrolysis [11,12,13]. Consistently, and irrespective of gender, age, race, length of frozen plasma storage time, or repeated sample freezing and thawing, over 95% of the initially added [ 3 H]-tyrosine LEU is recovered as the free labeled-aminoacid (after 30 min reaction; pH 7.4 and 37°C), with little formation of any of the other possible LEU degradation fragments [13]. Furthermore, various kinetic parameters examined of the plasmatic aminopeptidase LEU degradation reaction are not affected in various medical conditions such as chronic schizophrenia, migraine or drug addiction [13].…”

Section: Introductionmentioning

confidence: 99%

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In vitro Human Plasma Leucine<sup>5</sup>-Enkephalin Degradation Is Inhibited by a Select Number of Drugs with the Phenothiazine Molecule in Their Chemical Structure

Mosnaim¹,

Puente²,

Saavedra³

et al. 2002

Pharmacology

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A number of drugs with the phenothiazine molecule in their chemical structure inhibit in a dose-dependent manner human plasmatic aminopeptidase leucine⁵-enkephalin (LEU) metabolism. Half-life peptide degradation was significantly increased by thioridazine > fluphenazine > As-1397 [10-(α-diethylaminopropionyl)phenothiazine] ≧ promethazine ≧ chlorpromazine (final drug conc. 10^–4M); t1/2 (± SD) 21.2 ± 1.1, 19.6 ± 1.0, 17.2 ± 0.9, 17.1 ± 1.0, and 17.1 ± 1.1 min, respectively. Control and bacitracin (known aminopeptidase inhibitor) values were 11.8 ± 1.0 and 31.3 ± 1.7 min, respectively. These drugs significantly decreased (listed in the same order) LEU degradation initial velocity; Iv (± SD) 0.77 ± 0.2, 0.82 ± 0.2, 0.92 ± 0.3, 0.93 ± 0.2, 0.94 ± 0.3 pg LEU/min, respectively. Control and bacitracin 1.10 ± 0.3 and 0.20 ± 0.1 pg LEU/min, respectively. Values represent results from 5 samples, each obtained by pooling 6 individual plasmas (4 male and 2 female; n = 30 healthy, drug-free volunteers). However, neither the phenothiazines ethopropazine, methotrimeprazine, prochlorperazine and trifluoperazine nor the various commonly used heterocyclic antipsychotics tested, e.g., molindone, loxapine, clozapine, haloperidol, sulpiride and thiothixene inhibited plasma LEU degradation kinetics. Our results failed to show correlations between chemical structure, antipsychotic properties and ability to inhibit plasmatic aminopeptidase LEU degradation. Whereas, presence of the phenothiazine molecule appears to be necessary for enzyme inhibition, only five out of nine substituted phenothiazines tested exhibited this effect. Furthermore, there was a lack of correlation between phenothiazines antipsychotic properties and their capacity to inhibit aminopeptidase activity, a property shown by promethazine (antihistaminic) and As-1397 (selective butyrylcholinesterase inhibitor) but lacking in prochlorperazine and trifluoperazine. Our results provide information which could lead to the rational design of agents capable to modulate the bioavailability of enkephalin and other endogenous aminopeptidase-degraded peptides believed to be involved in the etiology and/or pathophysiology associated with various disease conditions. Whether their development could find useful pharmacological applications remains to be explored.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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In vitro Human Plasma Leucine<sup>5</sup>-Enkephalin Degradation Is Inhibited by a Select Number of Drugs with the Phenothiazine Molecule in Their Chemical Structure

Mosnaim¹,

Puente²,

Saavedra³

et al. 2002

Pharmacology

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“…Given the complexity of plasma samples, and the anticipated low abundance of GEs in plasma, the use of sample preparation methodology that allowed for the isolation and enrichment of low molecular weight plasma peptides was essential. In addition, because opioid peptides can be degraded by plasmatic proteases [22][23][24], the use of a protease inhibitor is imperative to ensure that peptide degradation does not continue after blood samples are obtained [25]. Enrichment and detection of GEs was accomplished by adapting existing ultrafiltration sample preparation methods [26,27], and then subjecting the low molecular weight plasma fraction to LC-MS/MS analysis.…”

Section: Introductionmentioning

confidence: 99%

Detection of Gluten Exorphin B4 and B5 in Human Blood by Liquid Chromatography-Mass Spectrometry/Mass Spectrometry

Pennington¹,

Dufresne²,

Fanciulli³

et al. 2007

TOSPECJ

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In vitro Methionine5-Enkephalin Degradation Kinetics by Human Brain Preparations

et al. 2007

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Incubation of [3H]-tyrosine methionine5-enkephalin (MET) with human brain preparations (100,000g supernatant; sections of the limbic system, thalamus, basal ganglia, cerebellum, and cortex) results in its rapid and complete degradation; over 95% of the initial labeled tyrosine is recovered as the free aminoacid within 10 min. Results show a considerable range in the peptide initial velocity (Iv) and half-life (t1/2) degradation values obtained from different brain sections of individual brains, either from the same or from different main brain areas. This relatively wide range of values was scattered, failing to identify consistent differences between the various brains areas studied. Differences in brain tissue storage time or repeated sample freezing and thawing failed to alter significantly either of these kinetic parameters of MET metabolism. Peptide degradation rate (optimum pH and temperature of 7.4 and 37 degrees C, respectively) was concentration-dependent inhibited by known aminopeptidase inhibitors (puromycin, bacitracin, and bestatin, and to a lesser extent by thioridazine). However, it was not significantly affected by either N-carboxymethyl phenyl leucine, captopril or thiorphan [dipeptidyl peptidase(s) or peptidyl dipeptidase(s) inhibitors, respectively]. A better understanding of the mechanisms regulating brain MET metabolism may contribute to the rational design of pharmacological strategies based in the modulation of its bioavailability.

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Degradation Kinetics of Leucine5-Enkephalin by Plasma Samples from Healthy Controls and Various Patient Populations

Cited by 18 publications

References 0 publications

In vitro Human Plasma Leucine<sup>5</sup>-Enkephalin Degradation Is Inhibited by a Select Number of Drugs with the Phenothiazine Molecule in Their Chemical Structure

In vitro Human Plasma Leucine<sup>5</sup>-Enkephalin Degradation Is Inhibited by a Select Number of Drugs with the Phenothiazine Molecule in Their Chemical Structure

Detection of Gluten Exorphin B4 and B5 in Human Blood by Liquid Chromatography-Mass Spectrometry/Mass Spectrometry

In vitro Methionine5-Enkephalin Degradation Kinetics by Human Brain Preparations

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