Opioid peptides in rat islets of Langerhans. Immunoreactive met- and leu-enkephalins and BAM-22P

Timmers, Kim I.; Voyles, Nancy R.; King, Clifford; Wells, Michael R.; Fairtile, Richard; Recant, Lillian

doi:10.2337/diabetes.35.1.52

Cited by 14 publications

(4 citation statements)

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“…of pituitary (Rossier et al, 1977); 1.62 pmol of [Met]enkephalin/pancreas (Timmers et al, 1986). Most of the [Met]enkephalin is present primarily in the form of high-molecular-mass enkephalins (such as BAM-22P) (Timmers et al, 1986). Very low amounts of MERF immunoreactivity have been reported in extracts of rat pancreas (Tang et al, 1982), but neither MERF nor MERGL were detectable in pancreas in our studies.…”

Section: Radioimmunoassaymentioning

confidence: 40%

“…of pituitary (Rossier et al, 1977). Large discrepancies, however, were observed for fl-endorphin measurements in extracts of pancreas; 1.72 fmnol/mg of protein (which includes highermolecular-mass forms) (Timmers et al, 1986); this is equivalent to 0.2 pmol/pancreas compared with 5.8 pmol/pancreas (Vuolteenaho et al, 1980) and 170 pmol/pancreas (Table 3). Differences between these values may be accounted for by the varied methods of tissue extraction used and by the specificity of the antibody for a particular opioid-peptide species.…”

Section: Radioimmunoassaymentioning

confidence: 88%

Section: Radioimmunoassaymentioning

confidence: 99%

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The occurrence and receptor specificity of endogenous opioid peptides within the pancreas and liver of the rat. Comparison with brain

Khawaja

Green

Thorpe

et al. 1990

Biochemical Journal

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Our observations that opioid peptides have direct effects on islet insulin secretion and liver glucose production prompted a search for endogenous opiates and their receptors in these peripheral tissues. ,u-, 6-and K-receptor-active opiates were demonstrated in brain, pancreas and liver extracts by displacement studies using selective ligands for the three opiateReceptor-active opiates in brain extracts exhibited a stronger preference for 6-opiate-receptor sites than for Iu and K sites. Pancreatic extract opiates demonstrated a similar activity at , and 6 sites, but substantially less at K sites. Liver extracts displayed similar selectivity for all three sites. The affinities of the receptor-active opiates for,u-, 6-and K-receptor subtypes displayed a rank order of potency: brain > pancreas > liver. Total immunoreactive f-endorphin and[Met5]enkephalin levels in liver and hepatocytes were greater than those in brain. Immunoreactive [MetI]enkephalin levels in pancreas were similar to, but /J-endorphin levels were substantially higher than, those in brain. 6 and K opiate-binding sites of high affinity were identified in crude membrane preparations of islets of Langerhans, but no specific opiate-binding sites could be demonstrated in liver membrane preparations. Immunoreactive dynorphin and /J-endorphin were demonstrated by immunogold labelling in rat pancreatic islet cells. No positive staining of liver sections for opioids was observed. These results suggest that the tissue content of opiate-receptor-active compounds in the pancreas and the liver is very significant and could contribute to the regulation of normal blood glucose levels.

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Section: Radioimmunoassaymentioning

confidence: 40%

Section: Radioimmunoassaymentioning

confidence: 88%

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The occurrence and receptor specificity of endogenous opioid peptides within the pancreas and liver of the rat. Comparison with brain

Khawaja

Green

Thorpe

et al. 1990

Biochemical Journal

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“…Opioid receptors are found in a wide variety of tissues, including the hypothalamicpituitary system, while their role and effect in endocrine regulation has been well-studied during the last decade 17,18 . All opioid receptors (MOP and DOP primarily, KOP in less extend) have been shown to be expressed in the pancreas and liver, while endogenous opioid peptides and their receptors have been shown to be present in pancreatic α-and β-cells [19][20][21] .…”

Section: Introductionmentioning

confidence: 99%

Opioid receptor-dependent modulation of insulin-release in pancreatic beta-cells

Paul¹,

Guven²,

Dietis

2014

PBJ

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In this study we aimed to look at the effects of opioid-receptor selective agonists and antagonists on insulin secretion in the pancreatic β-cell line RIN-5F. Cells were treated for 24 hours with 1μM of selective agonists (DAMGO for MOP, DPDPE for DOP, U50488 for KOP) in the presence or absence of 10μM of selective antagonists (CTOP for MOP, naltrindole for DOP, norBNI for KOP).An enzyme-based immunoassay was used to detect the amount of insulin in the supernatant, using a standard curve generated from known concentrations of rat insulin. A trypan blue viability assay was performed to assess the toxicity of each treatment and the secreted insulin was expressed as per 10 3 viable cells. Treatment with DAMGO or DPDPE caused an increase in secreted insulin by 94.2% and 76.3% respectively, compared to the non-treated controls. Cotreatment of DAMGO and CTOP was able to cancel out the agonists' effect. However, CTOP itself was able to increase insulin secretion by 72% when compared to control. These results suggest that opioid-induced insulin secretion may be based on G-protein independent mechanisms. In addition, none of the KOP-receptor selective ligands tested here were able to significantly affect insulin secretion compared to control, whereas naltrindole was highly toxic to pancreatic β-cells since it induced maximum cell death. Collectively, these findings suggest that MOP and DOP receptor-binding opioids might be more relevant in increasing insulin secretion from pancreatic β-cells than KOP receptor ligands.

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Rat Islet Endocrine Cells Contain Metand Leu-Enkephalins in High- and Low-Molecular-Weight Forms

Timmers

Voyles

King

et al. 1986

Neural and Endocrine Peptides and Receptors

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Opioid peptides in rat islets of Langerhans. Immunoreactive met- and leu-enkephalins and BAM-22P

Cited by 14 publications

References 0 publications

The occurrence and receptor specificity of endogenous opioid peptides within the pancreas and liver of the rat. Comparison with brain

The occurrence and receptor specificity of endogenous opioid peptides within the pancreas and liver of the rat. Comparison with brain

Opioid receptor-dependent modulation of insulin-release in pancreatic beta-cells

Rat Islet Endocrine Cells Contain Metand Leu-Enkephalins in High- and Low-Molecular-Weight Forms

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