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Biomedical subjects

L J Ge

Publications and source records attributed to L J Ge.

At least 19 recordsLinked to original sources
PubMed1998

Endomorphin 1 and 2, endogenous mu-opioid agonists, decrease systemic arterial pressure in the rat.

The endogenous opioid peptides, endomorphin 1 and 2, are newly isolated, potent, and selective mu-opioid receptor agonists. In the present study, responses to endomorphin 1 and 2 were investigated in the systemic vascular bed of the rat. Endomorphin 1 and 2 induced dose-related decreases in systemic arterial pressure when injected in doses of 1-30 nmol/kg i.v. In terms of relative vasodepressor activity, endomorphin 1 and 2 were approximately equipotent with each other and with the ORL1 ligand, nociceptin (orphanin FQ), and were about 10-fold more potent than met-enkephalin in decreasing systemic arterial pressure. Vasodepressor responses to endomorphin 1 and 2 and met-enkephalin, but not to nociceptin, were inhibited by the opioid receptor antagonist, naloxone. These results demonstrate that endomorphin 1 and 2 produce significant naloxone-sensitive decreases in systemic arterial pressure.

Analgesics, Opioid↗
PubMed1997

The endogenous mu-opioid receptor agonists endomorphins 1 and 2 have novel hypotensive activity in the rabbit.

The endogenous peptides endomorphins 1 and 2 are newly isolated, potent, and selective mu-opioid receptor agonists. In the present study, responses to the endomorphin peptides were investigated in the systemic vascular bed of the rabbit. Endomorphins 1 and 2 induced dose-related decreases in systemic arterial pressure when injected in doses of 1-30 nmol/kg i.v. In terms of relative vasodepressor activity, endomorphins 1 and 2 were similar to the ORL1 receptor ligand, nociceptin (Orphanin FQ), and met-enkephalin in decreasing systemic arterial pressure. Vasodepressor responses to endomorphins 1 and 2 were inhibited by the opioid receptor antagonist, naloxone, in a dose of 2 mg/kg i.v. These results demonstrate that endomorphins 1 and 2 have significant naloxone-sensitive, vasodepressor activity in the rabbit.

Analgesics, Opioid↗
PubMed1997

A potent and selective endogenous agonist for the mu-opiate receptor.

Peptides have been identified in mammalian brain that are considered to be endogenous agonists for the delta (enkephalins) and kappa (dynorphins) opiate receptors, but none has been found to have any preference for the mu receptor. Because morphine and other compounds that are clinically useful and open to abuse act primarily at the mu receptor, it could be important to identify endogenous peptides specific for this site. Here we report the discovery and isolation from brain of such a peptide, endomorphin-1 (Tyr-Pro-Trp-Phe-NH2), which has a high affinity (Ki = 360 pM) and selectivity (4,000- and 15,000-fold preference over the delta and kappa receptors) for the mu receptor. This peptide is more effective than the mu-selective analogue DAMGO in vitro and it produces potent and prolonged analgesia in mice. A second peptide, endomorphin-2 (Tyr-Pro-Phe-Phe-NH2), which differs by one amino acid, was also isolated. The new peptides have the highest specificity and affinity for the mu receptor of any endogenous substance so far described and they may be natural ligands for this receptor.

Amino Acid Sequence↗
PubMed1997

Endomorphin 1 and 2, endogenous ligands for the mu-opioid receptor, decrease cardiac output, and total peripheral resistance in the rat.

Endomorphin 1 and 2 are recently discovered endogenous ligands for the mu-opioid receptor. In the present study, responses to intravenous administration of endomorphin 1 and 2 were investigated in the systemic vascular bed of the rat. Endomorphin 1 and 2 induced dose-related decreases in systemic arterial pressure when injected in doses of 10-100 nmol/kg i.v.. The decreases in systemic arterial pressure in response to endomorphin 1 and 2 were associated with significant decreases in heart rate, cardiac output, and total peripheral resistance. The endogenous ligand for the ORL1 receptor, nociceptin/OFQ had similar effects on systemic arterial pressure, heart rate, cardiac output, and total peripheral resistance in the rat. Injections of isoproterenol (1 microgram/kg i.v.) and calcitonin gene-related peptide (CGRP; 0.3 nmol/kg i.v.), decreased systemic arterial pressure and total peripheral resistance. However these decreases in arterial pressure were associated with increases in heart rate and cardiac output. The results of the present study demonstrate that the endomorphin peptides have significant vasodilator activity in the systemic vascular bed of the rat and show that this response is associated with a decrease in heart rate and cardiac output.

Animals↗
PubMed1997

Isolation of relatively large amounts of endomorphin-1 and endomorphin-2 from human brain cortex.

Endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH2) were previously isolated from bovine brain. Both peptides showed the greatest selectivity and affinity for the mu opiate receptor of any endogenous substance found to date and may serve as natural ligands for the mu-opiate receptor. We have purified them from the fronto-parietal cortex of human brain tissue by solid phase extraction and high performance liquid chromatography. Peptide content was followed by a specific and sensitive radioimmunoassay with an antibody that was generated against endomorphin-1. The isolated endomorphins showed full biological activity. The tetrapeptides were found in human brain in much higher amounts than in bovine frontal cortex.

Amino Acid Sequence↗
PubMed1996

Binding of Tyr-W-MIF-1 (Tyr-Pro-Trp-Gly-NH2) and related peptides to mu 1 and mu 2 opiate receptors.

Two endogenous brain peptides (Tyr-W-MIF-1 (Tyr-Pro-Trp-Gly-NH2) and Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2)), a cyclized analog and two fragments of Tyr-W-MIF-1, and hemorphin (Tyr-Pro-Trp-Thr) were tested for binding to mu 1 and mu 2 opiate receptor. All these peptides bound to both mu 1 and mu 2 sites in assays optimized to discriminate these subtypes of the mu opiate receptor in membranes from bovine thalamus. The cyclized analog of Tyr-W-MIF-1, previously shown to have potency near that of Tyr-D-Ala-Gly-N-MePhe-Gly-ol (DAMGO) and morphine in producing analgesia after intracerebroventricular (i.c.v.) injection, bound to mu 1 and mu 2 sites with affinities similar to those of DAMGO. Tyr-W-MIF-1, previously shown to induce analgesia after i.c.v. injection but with much higher potency after intrathecal (i.t.) injection, also bound to both mu 1 and mu 2 sites with an affinity between that of morphiceptin and hemorphin. Although the highest ratios of Ki's for mu 2/mu 1 were shown by hemorphin, Tyr-W-MIF-1, and Tyr-W-MIF-1, none of the compounds were significantly different in selectivity. The results indicate that the relatively lower potency of Tyr-W-MIF-1 after i.c.v., compared with i.t. injection, is not due to a lack of binding to mu 1 sites. They suggest that it has relatively high efficacy at mu 2, but low efficacy at mu 1 sites, a possibility that might explain some of the novel properties of these peptides.

Animals↗
PubMed1994

Mu, delta, and kappa opiate receptor binding of Tyr-MIF-1 and of Tyr-W-MIF-1, its active fragments, and two potent analogs.

The relative binding to mu, delta, and kappa opiate receptors was characterized for the brain peptides Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2), Tyr-W-MIF-1 (Tyr-Pro-Trp-Gly-NH2), and two fragments of Tyr-W-MIF-1 (Tyr-Pro-Trp and Tyr-Pro-Trp-Gly) previously shown to have antagonist as well as agonist activity in the guinea pig ileum. Tyr-MIF-1 had relatively low affinity (Ki = 1 microM at the mu site) but high selectivity (400- and 700-fold greater affinity for mu over delta and mu over kappa binding). Tyr-W-MIF-1 (Ki = 71 nM at the mu site) showed higher affinity binding to all three sites than Tyr-MIF-1 while retaining 200-fold selectivity for mu over delta and kappa receptors. The affinity of the fragments of Tyr-W-MIF-1 was lower for mu but higher for delta receptors. We also tested two cyclized analogs of Tyr-W-MIF-1 that were about 200-fold more active than the parent compound in producing analgesia. These analogs showed higher affinity binding to all three opiate receptors. One of the analogs showed binding affinity to mu sites (Ki = 1.3 nM) that was within 3-fold of that of the potent analog of enkephalin, DAMGO. Thus, brain peptides with an N-terminal Tyr-Pro, rather than the Tyr-Gly-Gly-Phe sequence typical of other endogenous opiates, can provide high selectivity for mu opiate receptors. Analogs based on one of them, Tyr-Pro-Trp-Gly-NH2, show high affinity as well as potent analgesic activity.

Amino Acid Sequence↗
PubMed1994

Differential regulation of mu and delta opiate receptors by morphine, selective agonists and antagonists and differentiating agents in SH-SY5Y human neuroblastoma cells.

Mu and delta opiate receptor regulation by opiate agonists and antagonists was studied in the human neuroblastoma cell line SH-SY5Y. Morphine down-regulated both mu and delta receptors, but its effects on each subtype could be dissociated by use of specific antagonists. The selective mu antagonist D-Phe-Cys-Tyr-D-Trp-Arg-Pen-Thr-NH2 (CTAP) blocked the down-regulation of mu, but not delta receptors. Conversely, the delta antagonist (N,N-diallyl-Tyr-Aib-Aib-Phe-Leu-OH([N,N-diallyl-Tyr1, Aib2,3]Leu- enkephalin)] ICI 174,864 blocked morphine-induced down-regulation of delta but not mu receptors. These selective antagonists also were studied alone for their effects on both receptors. CTAP alone at doses of 0.1 microM and higher up-regulated mu receptors. CTAP did not affect delta receptors at 0.3 microM or less, but it down-regulated them at doses of 1 microM or more, apparently due to its delta agonist activity at higher doses, which was reversed by ICI 174,864. ICI 174,864 alone also showed complex effects on the two subtypes, up-regulating both mu and delta sites. Its effects were most selective at a low dose (0.1 microM), which upregulated delta sites with minimal effects on mu sites. The nonselective antagonist naloxone provided a more robust upregulation (> 40%) of both mu and delta receptors than either selective antagonist alone or in combination. The mu-to-delta ratio (1.4 to 1) was not altered by differentiation of the cells with retinoic acid, which up-regulated both mu and delta receptors. Differentiation with the phorbol agent 12-O-tetradecanoyl-phorbol-13-acetate, however, up-regulated mu, but not delta receptors. The selective mu agonist Tyr-Pro-MePhe-D-Pro-NH2 (PL017) down-regulated mu receptors with a half-maximal effect at 180 nM, but was without effect on delta receptors at concentrations up to 10 microM. Conversely, the selective delta agonist Tyr-D-Pen-Gly-Phe-D-Pen([D-Pen2,5]-enkephalin) (DPDPE) potently down-regulated delta receptors, producing half-maximal decreases at 0.5 nM. At doses above those that reduced the maximum binding of [3H]pCl-DPDPE binding to the delta site, DPDPE also induced an apparent loss of affinity (increased Kd) at the delta site. It was without effect on mu receptors, however, at doses up to 10 microM. Thus, down-regulation of mu and delta receptors was homologous, because selective agonists down-regulated their respective receptors without effect on the heterologous opiate receptor.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1993

Mu opiate receptor down-regulation by morphine and up-regulation by naloxone in SH-SY5Y human neuroblastoma cells.

The human neuroblastoma cell line SH-SY5Y was used to demonstrate morphine-induced down-regulation and naloxone-induced up-regulation of opiate receptors in a mu receptor containing neuronally derived preparation capable of desensitization to morphine. Chronic exposure to morphine decreased the number but not the affinity of mu opiate receptors in SH-SY5Y cells. Differentiation of the cells with retinoic acid or with the phorbol agent TPA (12-O-tetradecanoyl-phorbol-13-acetate) increased the number of mu receptors. Morphine-induced down-regulation, however, was observed in the absence of differentiation as well as after differentiation with retinoic acid or TPA. The decrease in the number of receptors was related to time of exposure, with a half-maximum disappearance time (T1/2) of about 3 hr during the initial phase. The receptor decrease was near maximum at 24 hr with no further significant change up to 72 hr. The loss of [3H] DAMGO ([3H]Tyr-D-Ala-Gly-N-Me-Phe-Gly-ol) binding was also dose-dependent, with reductions occurring at 0.3, 1 and 10 microM. The loss of receptors was dependent on temperature, with reductions at 37 but not 23 degrees C. The down-regulation was blocked by naloxone and the mu-selective antagonist CTOP (D-Phe-Cys-Tyr-D(-Trp-)Orn-Thr-Pen-Thr-NH2), but not by the delta antagonist ICI 174864 ([N,N-diallyl-Tyr1,Aib2,3]Leu-enkephalin). Cholinergic ([3H]quinclidinyl benzilate) binding was not affected by the morphine treatment, indicating that the down-regulation was homologous for opiate receptors. In SH-SY5Y cells, unlike other cell models, the opiate antagonist naloxone upregulated mu receptors by more than 50%.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

Tyr-MIF-1 binding in brain is not altered by ligands selective for the GABAA/benzodiazepine receptor.

Binding of benzodiazepines to the benzodiazepine gamma-aminobutyric acid (GABA) receptor-chloride channel complex has been shown to be altered by Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2). This raised the possibility of allosteric binding interactions between Tyr-MIF-1 sites and the GABAA receptor complex. We tested this possibility in rat brain by examining the binding of Tyr-MIF-1 to brain membranes in the presence of clonazepam, GABA, a combination of clonazepam and GABA, RO15788, or picrotoxinin. None of the tested substances affected Tyr-MIF-1 binding. We also tested mouse cortex for changes in Tyr-MIF-1 binding in the presence of ligands that bind to the GABA/benzodiazepine/chloride channel complex. Clonazepam, flunitrazepam, RO15788, and picrotoxinin at concentrations ranging from 10(-13) to 10(-5) M, each in the absence or presence of GABA at concentrations ranging from 10(-9) to 10(-5) M, each in the absence or presence of GABA at concentrations ranging from 10(-9) to 10(-6) M, did not significantly alter the binding of Tyr-MIF-1. The results indicate that simple bidirectional allosteric interactions between Tyr-MIF-1 binding sites and benzodiazepine, GABA or chloride channel binding sites are not likely to be the mechanism by which Tyr-MIF-1 affects binding at this complex.

Animals↗
PubMed1990

Hemorphins, cytochrophins, and human beta-casomorphins bind to antiopiate (TYR-MIE-1) as well as opiate binding sites in rat brain.

Novel peptides with opiate activity, derived from endogenous sources (human and bovine casomorphins from milk, hemorphins from hemoglobin, and cytochrophins from mitochondrial cytochrome b), were tested for their ability to inhibit binding of the brain peptide Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2) to its high affinity sites in rat brain. The order of potency in inhibiting binding of 125I-Tyr-MIF-1 was: hemorphin and bovine casomorphins greater than Tyr-MIF-1 greater than cytochrophins greater than human casomorphins. Naloxone and DAMGO were ineffective at inhibiting Tyr-MIF-1 binding. The results provide evidence that, in addition to their ability to bind to mu opiate receptors, these novel endogenous peptides with opiate activity and a peptide (Tyr-MIF-1) with antiopiate properties also bind to a non-opiate site labeled by Tyr-MIF-1. These sites could be involved in a balance between opiate and antiopiate peptides.

Amino Acid Sequence↗
PubMed1989

Chronic, but not acute, administration of morphine alters antiopiate (Tyr-MIF-1) binding sites in rat brain.

Opiate addiction could involve a change in the binding of endogenous antiopiates. A candidate for such a role is Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2), a brain peptide that can antagonize exogenous and endogenous opiates and bind to opiate receptors. Its primary action, however, may be through its own binding site in brain, which we now report is altered by chronic administration of morphine. Rats given morphine pellets had reduced binding of both iodinated and tritiated Tyr-MIF-1 on day 5, when substantial tolerance is evident. In contrast, mu and delta opiate receptors were increased. Acute injection of an analgesic dose of morphine did not reduce Tyr-MIF-1 binding, indicating that chronic administration is required for the change. These findings open new approaches to the study of addiction by focusing on antiopiate activity.

Animals↗
PubMed1982

Suppression of ovulation in the rat by an orally active antagonist of luteinizing hormone-releasing hormone.

A synthetic antagonist of luteinizing hormone-releasing hormone blocked ovulation in rats in a dose-dependent manner when given by gavage on the afternoon of proestrus. Ovulation was delayed for at least 1 day in all animals given 2 milligrams of antogonist and in some of the animals treated with 1 or 0.5 milligram. Oral administration of 2 milligrams also blocked the preovulatory surge of luteinizing hormone. This demonstration that antagonists of luteinizing hormone-releasing hormone can have oral antiovulatory activity clearly enhances their therapeutic potential.

Administration, Oral↗
PubMedDate not supplied

Chemical characterization of angiotensin I in porcine follicular fluid.

In the search for novel neuropeptides in porcine follicular fluid (pff) using smooth muscle contractile activity as a response parameter, a substance with a marked activity was isolated in a pure form. By amino acid analysis and sequential study, this substance has been chemically revealed to be angiotensin I. A much smaller amount of additional activity was isolated and found to be angiotensin II, as determined by radioimmunoassay. Radioimmunoassays for angiotensin I and II confirmed that the amount of angiotensin I determined was much greater than that of angiotensin II. A comparative study of the extractions, however, indicated a large amount of angiotensin I had been generated from angiotensinogen by endogenous renin in the follicular fluid which could be activated during extraction and ultrafiltration at a low pH. These findings are consistent with the previous reports that described a high concentration of prorenin in the follicular fluid, acid activation of prorenin to renin and the subsequent generation of angiotensin I from endogenous angiotensinogen.

Amino Acid Sequence↗