Disease relevance of Leu-enkephalin

• In four cases of pheochromocytoma marked difference in Met- and Leu-enkephalin contents was found between medullary and extramedullary tumors [1].
• Third, hyperglycemia augments BLI secretion in response to the neuropeptides VIP and Leu-enkephalin [2].
• The elevation of plasma Met-enkephalin and beta-endorphin preceded the onset of hyperinsulinism, but the elevation of plasma Leu-enkephalin did not [3].
• Leu-enkephalin levels were decreased in the putamen and were undetectable in the substantia nigra in Parkinson's disease [4].
• Thus, the onset of overt obesity between 4 and 6 wk of age was accompanied by a marked rise in both pancreatic beta-endorphin and pituitary Leu-enkephalin; similar elevations in these parameters have been reported previously in C57BL/6J ob/ob mice at approximately 12 wk of age.(ABSTRACT TRUNCATED AT 250 WORDS)[5]

Psychiatry related information on Leu-enkephalin

• Differential effect of posttraining naloxone, beta-endorphin, leu-enkephalin and electroconvulsive shock administration upon memory of an open-field habituation and of a water-finding task [6].
• A comparison was carried out of the effectiveness of intracerebroventricular or intraperitoneal administration of Leu-enkephalin to affect acquisition of a one-way active avoidance response, locomotor activity or shock sensitivity [7].
• Immediate post-training i.p. injection of Met-enkephalin, Leu-enkephalin or des-Tyr-Met-enkephalin, caused retrograde amnesia for a shuttle avoidance task in rats [8].
• Prolonged intermittent footshock stress decreases Met and Leu enkephalin levels in brain with concomitant decreases in pain threshold [9].

High impact information on Leu-enkephalin

• CD10/NEP hydrolyses several naturally occurring peptides, including the endogenous opioid pentapeptides Met- and Leu-enkephalin [10].
• Polymorphism and absence of Leu-enkephalin sequences in proenkephalin genes in Xenopus laevis [11].
• There is good evidence that the large amounts of Leu-enkephalin found in the adrenal medulla are generated from the precursor proenkephalin, but as yet prodynorphin has not been shown to be processed to yield Leu-enkephalin [12].
• The amino acid sequence of the opioid peptide Leu-enkephalin is found within several larger peptides, which are generated from the precursors proenkephalin and prodynorphin [12].
• A dynorphinergic pathway of Leu-enkephalin production in rat substantia nigra [12].

Chemical compound and disease context of Leu-enkephalin

• In contrast, [F/G]NC(1-13)NH2 did not alter the hypotension induced by bradykinin or endomorphin-1 (a micro-receptor agonist), and the bradycardia induced by leu-enkephalin (a delta-receptor agonist) or U504885 (a synthetic kappa-receptor agonist) [13].
• In some animals the natural syndrome was enhanced by the prior administration of DL-allylglycine, 100--200 mg/kg, i.v. Met- or Leu-enkephalin, 1--10 mg, i.c.v., did not lead to any manifest focal or generalized seizure discharges [14].
• One-week SAD rats were characterized by hypertension, tachycardia, increased norepinephrine content, and decreased beta-endorphin and leu-enkephalin content in hypothalamus and medulla oblongata, and increased plasma levels of arginine-vasopressin [15].
• It has been observed that a vasopressin receptor antagonist attenuates hypoxic hyperemia in fetal sheep, whereas methionine enkephalin (Met) and leucine enkephalin (Leu) contribute to hypoxia-induced pial artery dilation in newborn pigs [16].
• 3. Injection of a small dose of Leu-enkephalin, which is devoid of effect on mouse motility, prior to an acute sedative dose of ethanol to tamoxifen pretreated female mice counteracted ethanol-produced suppression of motor activity [17].

Biological context of Leu-enkephalin

• However, all reported assays show some degree of cross-reaction with Leu-enkephalin and unequivocal differentiation between the two enkephalins and the larger endorphins has not always been possible [18].
• Leu-enkephalin purification from E. coli cells carrying the plasmid with fused synthetic leu-enkephalin gene [19].
• Met- and leu-enkephalin are resistant to hydrolysis [20].
• Leu-enkephalin (10(-5) M) did not modify the latency or the amplitude of the action potentials evoked with low frequency of stimulation (0.5 Hz) or with 'vasopressin'-like bursts [21].
• A brain-targeted chemical delivery system (CDS) based on retrometabolic drug design was applied to a Leu-enkephalin analogue, Try-D-Ala-Gly-Phe-D-Leu (DADLE) [22].

Anatomical context of Leu-enkephalin

• Met- and Leu-enkephalin-like material occurred in considerable quantities in carotid body extracts and enkephalin-like immunoreactivity was localised in type I cells [23].
• Extracts of neurohypophysis have been shown to contain substantial amounts of Met- and Leu-enkephalin, and Leu-enkephalin-immunoreactive (IR) nerve fibres originating in the magnocellular hypothalamic nuclei have been described in the neural lobe, where the two hormones are secreted [24].
• These results suggest the physiological roles of Met- and Leu-enkephalin in sympathetic nervous system and adrenal glands and their pathophysiological significances in pheochromocytomas [1].
• Bovine adrenal chromaffin granules have been shown to contain, in addition to Met-enkephalin and Leu-enkephalin, at least three small peptides with opiate receptor activity [25].
• It is likely that a family of Leu-enkephalin-like peptides is present in monkey spinal cord and that the labeled elements may contain any or all of these substances [26].

Associations of Leu-enkephalin with other chemical compounds

• Met-enkephalin was approximately 74% of Met-enkephalin-LI, whereas Leu-enkephalin was approximately 30% of Leu-enkephalin-LI in human adrenal medulla [1].
• We found an excellent quantitative correlation between the affinities of the various peptides determined by binding assays and their functional potency tested on catecholamine secretion: bovine chromostatin greater than human chromostatin greater than CGA much greater than rat chromostatin, pancreastatin, CAP-14, substance P, and Leu-enkephalin [27].
• Furthermore, in thin serial sections of these glands, dopamine beta-hydroxylase, phenylethanolamine N-methyltransferase, and leu-enkephalin appeared to be colocalized in the same cells of the adrenal medulla [28].
• Treatment of olfactory bulbs with cholera toxin did not alter the stimulation of adenylate cyclase by Leu-enkephalin [29].
• Our findings indicate that the juxtapositions between LHRH-IR and leu enkephalin-IR neurons may be functional synapses forming the morphological substrate of the leu-enkephalin-modulated LHRH secretion in the human diencephalon [30].

Gene context of Leu-enkephalin

• ECE-1, unlike neprilysin, was found to have minimal activity against substrates smaller than hexapeptides, such as Leu-enkephalin [31].
• Taken together, these data suggest that CPE is completely inactive in the Cpefat/Cpefat mice, and that all of the CPE-like activity is due to other carboxypeptidases such as carboxypeptidase D. Levels of Leu-enkephalin in Cpefat/Cpefat mouse brain are approximately 5-fold lower than those in control brain [32].
• No immunoreactivity was obtained either in the cerebral ganglion or in the alimentary tract with antibodies to leu-enkephalin, met-enkephalin, CCK, growth hormone, ACTH, CLIP and GIP [33].
• A highly selective assay for neutral endopeptidase based on the cleavage of a fluorogenic substrate related to Leu-enkephalin [34].
• The role of neuropeptides in the regulation of adrenal vascular tone: effects of vasoactive intestinal polypeptide, substance P, neuropeptide Y, neurotensin, Met-enkephalin, and Leu-enkephalin on perfusion medium flow rate in the intact perfused rat adrenal [35].

Analytical, diagnostic and therapeutic context of Leu-enkephalin

• Existence of authentic Met- and Leu-enkephalin was confirmed by reverse-phase high-performance liquid chromatography [1].
• With the same Leu-enkephalin antiserum as used in the immunocytochemistry, a peptide physicochemically similar to intact Leu-enkephalin and two larger Leu-enkephalin-like peptides were identified in monkey spinal cord extracts [26].
• Fasting human plasma immunoreactive leu-enkephalin (ir-leu-enkephalin) measured by radioimmunoassay averages 54+/-10 pg/ml [36].
• Crystal packing calculations have been carried out on a substantial number of conformations of Leu-enkephalin; namely, those obtained both from crystal structures and from energy minimizations on isolated molecules, and with and without waters of crystallization [37].
• HPLC analysis identified the majority of the postmortem-induced immunoreactive material as Met- and Leu-enkephalin [38].

References