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Experientia Jul 1985In swine, cerebral blood flow was documented by a left ventricular injection of radiolabeled 15-micron spheres. Utilizing this procedure, the effect of the putative...
In swine, cerebral blood flow was documented by a left ventricular injection of radiolabeled 15-micron spheres. Utilizing this procedure, the effect of the putative neurotransmitter methionine-enkephalin on regional cerebral blood flow was systemically evaluated. Our results revealed that a peripheral infusion of methionine enkephalin into miniature swine significantly increased cerebral blood flow in the basal ganglia, cerebellum, pons, inferior parietal cortex and frontal cortex. Non-significant increases were observed in the hippocampus, occipital cortex and medulla oblongata while no effect on blood flow was observed in the pituitary gland. Significance of these results in the potential role of methionine enkephalin as a modulator of blood flow to the brain.
Topics: Animals; Cerebrovascular Circulation; Enkephalin, Methionine; Regional Blood Flow; Swine
PubMed: 4007131
DOI: 10.1007/BF01970019 -
International Immunopharmacology Oct 2019Endogenous opioids are neuro-peptides with multifunctional properties. Historically, opioids are used to mediate pain; however, excess opiate consumption can lead to... (Review)
Review
Endogenous opioids are neuro-peptides with multifunctional properties. Historically, opioids are used to mediate pain; however, excess opiate consumption can lead to addiction. One endogenous opioid, methionine enkephalin (MENK), was reported to modulate cell growth, MENK was identified as an opioid growth factor (OGF) that interacts with the OGF receptor (OGFr) and regulates cell proliferation. Further, opioid antagonists, including naltrexone and naloxone are widely used to reverse drug and alcohol overdoses. Naltrexone (NTX) acts on all opioid receptors, blocking the interaction between OGF and OGFr, and thus influencing cell growth. During the last decades, insights have been made concerning the interaction between OGF and OGFr, confirming that both opioids and opioid antagonists have an important role in balancing host homeostasis, host immunity and mediating cancer therapy. This review provides insight into the interactions between OGF and OGFr in the treatment of cancers.
Topics: Animals; Enkephalin, Methionine; Humans; Naltrexone; Narcotic Antagonists; Neoplasms
PubMed: 31404891
DOI: 10.1016/j.intimp.2019.105785 -
Journal of Neurochemistry Jul 1983The distribution of the opioid peptide methionine-enkephalin-arginine6-phenylalanine7 (M-Enk-Arg6-Phe7) has been investigated in various structures of the rat brain by...
The distribution of the opioid peptide methionine-enkephalin-arginine6-phenylalanine7 (M-Enk-Arg6-Phe7) has been investigated in various structures of the rat brain by using a highly specific radioimmunoassay (RIA). Immunoreactive M-Enk-Arg6-Phe7 has been further characterized by high performance liquid chromatography. The levels of M-Enk-Arg6-Phe7 in various structures of the rat brain were compared with the levels of several other opioid peptides, including methionine-enkephalin (M-Enk), leucine-enkephalin (L-Enk), dynorphin 1-13, and alpha-neoendorphin, which were also measured by RIA. There was a close relationship between the distribution of M-Enk-Arg6-Phe7 immunoreactive material (ir), M-Enk ir, and L-Enk ir. The distribution of dynorphin 1-13 ir and alpha-neoendorphin ir appeared to be distinct from that of the enkephalin group. These results are in agreement with recent reports on the cloning and sequencing of the c-DNA coding for the prohormones, in which it has been hypothesized that M-Enk-Arg6-Phe7 and M-Enk are synthesized by the same precursor, called proenkephalin, and that dynorphin-related peptides and alpha-neoendorphin arise from a separate precursor, prodynorphin.
Topics: Amino Acid Sequence; Animals; Brain Chemistry; Chromatography, High Pressure Liquid; Endorphins; Enkephalin, Leucine; Enkephalin, Methionine; Enkephalins; Male; Pituitary Hormones, Anterior; Pro-Opiomelanocortin; Protein Precursors; Radioimmunoassay; Rats; Rats, Inbred Strains; Tissue Distribution
PubMed: 6688089
DOI: 10.1111/j.1471-4159.1983.tb11827.x -
Life Sciences Jun 1985The preproenkephalin A molecule from the adrenal medulla contains the opioid peptides methionine-enkephalin (Met-ENK), leucine-enkephalin (Leu-ENK),... (Comparative Study)
Comparative Study
The preproenkephalin A molecule from the adrenal medulla contains the opioid peptides methionine-enkephalin (Met-ENK), leucine-enkephalin (Leu-ENK), methionine-enkephalin-Arg6-Phe7 (heptapeptide), and methionine-enkephalin-Arg6-Gly7-Leu8 (octapeptide). In the conscious, chronically instrumented dog, Met-ENK and Leu-ENK simultaneously increase heart rate and systemic arterial pressure following intravenous administration. In 19 of 23 dogs, heptapeptide produced a response identical to Met-ENK and Leu-ENK, which was inhibited by naloxone but unaffected by the dipeptidyl carboxypeptidase inhibitor SQ20881. However, in four dogs, heptapeptide produced only a fall in systemic pressure associated with an increase in heart rate despite characteristic Met-ENK responses in the same dogs; naloxone did not appear to alter this hypotensive response. Octapeptide produced slight increases in systemic pressure and heart rate. These data suggest that heptapeptide may possess intrinsic cardiovascular activity at opiate receptors; however, in certain dogs, non-opiate mechanisms, perhaps histamine release, may predominate.
Topics: Animals; Blood Pressure; Cardiovascular System; Dogs; Endopeptidases; Enkephalin, Methionine; Heart Rate; Naloxone; Structure-Activity Relationship
PubMed: 3889529
DOI: 10.1016/0024-3205(85)90330-3 -
Immunoreactive evidence of beta-endorphin and methionine-enkephalin-Arg-Gly-Leu in human tooth pulp.Life Sciences 1989For the first time, beta-endorphin-like immunoreactivity (BE-LI) has been measured in human tooth pulp. Separation of peptides from pulp tissue was achieved by acid...
For the first time, beta-endorphin-like immunoreactivity (BE-LI) has been measured in human tooth pulp. Separation of peptides from pulp tissue was achieved by acid extraction followed by chromatographic separation through a Sep-Pak disposable cartridge. Reversed phase high performance liquid chromatographic (RP-HPLC) was performed on the peptide-rich fractions for further peptide separation. Radioreceptor assay (RRA) data of the HPLC fractions was used to construct a profile of opioid-receptor active peptides. Radioimmunoassay (RIA) data provided further information. Following acute mechanical stress, a monotonic decrease in BE-LI concentrations was evident according to a four bicuspid extraction order.
Topics: Adolescent; Adult; Child; Chromatography, High Pressure Liquid; Dental Pulp; Enkephalin, Methionine; Female; Humans; Male; Neuropeptides; Radioimmunoassay; Radioligand Assay; beta-Endorphin
PubMed: 2529409
DOI: 10.1016/0024-3205(89)90152-5 -
NIDA Research Monograph 1988
Review
Topics: Analgesics; Animals; Enkephalin, Methionine; Female; Guinea Pigs; In Vitro Techniques; Male; Mice; Morphine; Muscle Contraction; Structure-Activity Relationship
PubMed: 3150774
DOI: No ID Found -
Life Sciences 1983Using specific radioimmunoassays(RIAs) for methionine-enkephalin(Met-Enk), leucine-enkephalin(Leu-Enk), methionine-enkephalin-Arg6-Gly7-Leu8 (Met-Enk-Arg-Gly-Leu) and... (Comparative Study)
Comparative Study
Parallel distribution of methionine-enkephalin-Arg6-Gly7-Leu8 with methionine-enkephalin, leucine-enkephalin and methionine-enkephalin-Arg6-Phe7 in human and bovine brains.
Using specific radioimmunoassays(RIAs) for methionine-enkephalin(Met-Enk), leucine-enkephalin(Leu-Enk), methionine-enkephalin-Arg6-Gly7-Leu8 (Met-Enk-Arg-Gly-Leu) and methionine-enkephalin-Arg6-Phe7 (Met-Enk-Arg-Phe), we studied the regional distribution of these opioid peptides in human and bovine brains. Met-Enk-Arg-Gly-Leu was distributed in parallel with Met-Enk, Leu-Enk and Met-Enk-Arg-Phe in human and bovine brains. The ratios of molar concentrations of these peptides are almost constant in various regions of human and bovine brains and similar to the ratio of these peptides contained in preproenkephalin A. Gel exclusion chromatography and HPLC coupled with respective RIAs showed the existence of authentic peptides without any detectable high molecular weight forms. These results indicate the parallel distribution of Met-Enk-Arg-Gly-Leu with Met-Enk, Leu-Enk and Met-Enk-Arg-Phe in various regions of human and bovine brains and further suggest that these opioid peptides are derived from the same precursor as that in the adrenal medulla and that the processing of preproenkephalin A is almost complete in human and bovine brains.
Topics: Animals; Brain Chemistry; Cattle; Chromatography, High Pressure Liquid; Enkephalin, Leucine; Enkephalin, Methionine; Humans; Species Specificity
PubMed: 6664241
DOI: 10.1016/0024-3205(83)90445-9 -
Experimental Eye Research Dec 1990Native methionine enkephalin and methionine enkephalin generated proteolytically from a larger peptide were both identified and quantified from bovine cornea by negative...
Native methionine enkephalin and methionine enkephalin generated proteolytically from a larger peptide were both identified and quantified from bovine cornea by negative ion fast atom bombardment-mass spectrometry. The corneal peptides were purified initially be reverses-phase high performance liquid chromatography and identified tentatively by radioreceptor assay and/or radioimmunoassay.
Topics: Animals; Cattle; Chromatography, High Pressure Liquid; Cornea; Enkephalin, Methionine; Radioligand Assay; Spectrometry, Mass, Fast Atom Bombardment
PubMed: 2265678
DOI: 10.1016/0014-4835(90)90051-u -
General Pharmacology 19881. Incubation of [3H]tyrosine methionine-enkephalin (6 x 10(-9) M final concentration) with human platelet-poor plasma (1:9 ratio to Trizma Base buffer, pH 7.4) results...
1. Incubation of [3H]tyrosine methionine-enkephalin (6 x 10(-9) M final concentration) with human platelet-poor plasma (1:9 ratio to Trizma Base buffer, pH 7.4) results mostly (greater than 95%) in hydrolysis of the tyrosyl-glycine peptide bond. This enzymatic reaction is essentially completed within 90 min, showing a half-life, Km and Vmax of 12.8 +/- 2.5 min, 0.70 +/- 0.01 mM and 17.90 +/- 1.05 mumol/L/min, respectively. These values are comparable to those previously reported for the human plasma degradation of leucine-enkephalin. 2. As expected hydrolysis of the methionine-enkephalin tyrosyl-glycine peptide bond was blocked by the known aminopeptidase inhibitors bestatin and puromycin (IC50 1.2 +/- 0.4 and 4.3 +/- 2.4 microM, respectively) but not by either thiorphan or captopril. 3. Neither the storing (up to 60 days) nor the freezing and thawing (up to ten times during a 60 days periods) significantly changed the above kinetic parameters, showing the stability of the plasma methionine-enkephalin degrading aminopeptidase.
Topics: Chromatography, Thin Layer; Enkephalin, Methionine; Humans; Leucine; Puromycin
PubMed: 3215483
DOI: 10.1016/0306-3623(88)90137-1 -
Endocrinology Jan 1991The current study examined the presence of immunoreactive methionine-enkephalin (ir-MENK) in porcine uterine fluid and endometrial extracts, characterized ir-MENK...
The current study examined the presence of immunoreactive methionine-enkephalin (ir-MENK) in porcine uterine fluid and endometrial extracts, characterized ir-MENK biochemically, and investigated the effect of ovarian steroids on uterine secretion of ir-MENK. Porcine uterine fluid was collected by flushing the uterine lumen with saline. Endometrial tissues were extracted with acetic acid. Both uterine fluid and endometrial extracts exhibited inhibition curves parallel to that of authentic MENK in the MENK RIA system. Sephadex G-15 gel filtration chromatographic profiles indicated that both concentrated uterine fluid and endometrial extracts contained two peaks of ir-MENK, a major peak which coeluted with standard MENK, and a minor peak eluting near the void volume (Vo). Reverse phase-HPLC chromatographic profiles also demonstrated two peaks of ir-MENK for concentrated uterine fluid and endometrial extracts, a major peak which coincided with standard MENK, plus a highly hydrophilic peak. The effect of ovarian steroids on the uterine secretion of ir-MENK was examined by measuring ir-MENK in uterine fluids from cyclic and pregnant gilts as well as ovariectomized, ovarian steroid-treated gilts. Day effects (P less than 0.01) were detected for cyclic and pregnant gilts, since values for ir-MENK increased between days 8 and 14 after onset of estrus. In ovariectomized gilts, treatment with progesterone (P4) increased the uterine secretion of ir-MENK (202 +/- 9 vs. 65 +/- 4 pg/ml for control, P less than 0.05). The combined treatment of P4 and estradiol did not further enhance secretion of ir-MENK, while treatment with estradiol did not alter ir-MENK levels relative to values for control gilts. These results indicate the presence of ir-MENK in porcine uterine fluid and endometrium, and suggest that uterine secretion of ir-MENK is regulated primarily by P4.
Topics: Animals; Chromatography, Gel; Endometrium; Enkephalin, Methionine; Estradiol; Female; Pregnancy; Progesterone; Radioimmunoassay; Swine; Uterus
PubMed: 1986919
DOI: 10.1210/endo-128-1-21