Comparison of the effects of [leucine]enkephalin and angiotensin on hepatic carbohydrate and cyclic nucleotide metabolism

Hothi, S K; Leach, R.; Titheradge, Michael A.

doi:10.1042/bj2490669

Cited by 10 publications

(10 citation statements)

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“…A centrally mediated sympathetic connection between opioid peptides and glucose homoeostasis has been established for some time (Bodo et al, 1937;Vassalle, 1961;Feldberg & Smyth, 1977;Pfeiffer et al, 1983); however, evidence for a direct peripheral action of opiates in the regulation of hepatic glucose production and on glucose homoeostasis through pancreaticislet hormone secretion has only more recently been reported (Ipp et al, 1978;Green et al, 1980Green et al, , 1983aAllan et al, 1983;Leach et al, 1985; Leach & Titheradge, 1986;Hothi et al, 1988). /J-Endorphin, [Met5]enkephalin, [Leu5]enkephalin and dynorphin A-(1-13)-peptide have been shown to regulate insulin, glucagon and somatostatin release from isolated islets of Langerhans by a naloxone-reversible mechanism (Ipp et al, 1978;Green et al, 1980Green et al, , 1983aHermansen, 1983;Curry et al, 1987;Toyota et al, 1985).…”

Section: Introductionmentioning

confidence: 99%

“…/8-Endorphin (Matsumura et al, 1984), [Met5]enkephalin, [Leu5]enkephalin and dynorphin A-(l-l 3)-peptide (Allan et al, 1983;Leach et al, 1985;Leach & Titheradge, 1986) have all been shown to induce a rapid dose-dependent stimulation of both glycogenolysis and glycogenesis. The mechanism of action of ,-endorphin has been attributed to a rise in cyclic AMP (Matsumura et al, 1984), whereas the enkephalins and dynorphin decrease cyclic AMP levels and adenylate cyclase activity and increase inositol lipid turnover and cytosolic Ca2l (Leach & Titheradge, 1986;Leach et al, 1986;Hothi et al, 1988). Wajda et al (1976) have identified the existence of an opiate-like factor in Tris/HCl extracts of rat liver by its ability to displace [3H]naloxone and [3H]dihydromorphine from rat brain membrane receptors in a dose-dependent fashion.…”

Section: Introductionmentioning

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: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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“…Several in vitro hepatocyte studies have shown that angiotensin II stimulates glycogen phosphorylase activity (4)(5)(6) and gluconeogenesis (7)(8)(9)(10). Recently, we have shown that RAS involvement in blood glucose regulation is of physiological significance, with angiotensin II producing a dose-dependent hyperglycemic response (1).…”

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The hyperglycemia induced by angiotensin II in rats is mediated by AT1 receptors

Machado

Marubayashi

Reis

et al. 1998

Braz J Med Biol Res

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We have shown that the renin-angiotensin system (RAS) is involved in glucose homeostasis during acute hemorrhage. Since almost all of the physiological actions described for angiotensin II were mediated by AT 1 receptors, the present experiments were designed to determine the participation of AT 1 receptors in the hyperglycemic action of angiotensin II in freely moving rats. The animals were divided into two experimental groups: 1) animals submitted to intravenous administration of angiotensin II (0.96 nmol/100 g body weight) which caused a rapid increase in plasma glucose reaching the highest values at 5 min after the injection (33% of the initial values, P<0.01), and 2) animals submitted to intravenous administration of DuP-753 (losartan), a nonpeptide antagonist of angiotensin II with AT 1 -receptor type specificity (1.63 µmol/100 g body weight as a bolus, iv, plus a 30-min infusion of 0.018 µmol 100 g body weight -1 min -1 before the injection of angiotensin II), which completely blocked the hyperglycemic response to angiotensin II (P<0.01). This inhibitory effect on glycemia was already demonstrable 5 min (8.9 ± 0.28 mM, angiotensin II, N = 9 vs 6.4 ± 0.22 mM, losartan plus angiotensin II, N = 11) after angiotensin II injection and persisted throughout the 30-min experiment. Controls were treated with the same volume of saline solution (0.15 M NaCl). These data demonstrate that the angiotensin II receptors involved in the direct and indirect hyperglycemic actions of angiotensin II are mainly of the AT 1 -type. Key wordsIn addition to affecting fluid volume, electrolytes and hemodynamic states, the renin-angiotensin system (RAS) is also involved in the regulation of metabolic and endocrine function, especially blood glucose homeostasis (1-3). Several in vitro hepatocyte studies have shown that angiotensin II stimulates glycogen phosphorylase activity (4-6) and gluconeogenesis (7-10). Recently, we have shown that RAS involvement in blood glucose regulation is of physiological significance, with angiotensin II producing a dose-dependent hyperglycemic response (1). In contrast, intravenous infusion of an angiotensin II peptide-analog antagonist, [1-sar,8-thr]-angiotensin II (sarthran), had an

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“…Male Sprague-Dawley rats ( 180-200 g) were treated with lipopolysaccharide from Salmonellu typhimurium ( 4 mg/kg intraperitoneally) or pyrogen-free saline and starved for 18 h. Hepatocytes were prepared as described previously [7] and were incubated in Krebs-Henseleit bicarbonate buffer (40 mg wet wt./ml) for 30 min in the presence of 18 mMlactate/2 mwpyruvate. Samples for F 2,6-BP measurement were prepared and assayed as in [8].…”

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confidence: 99%

“…PFK-2 and F 2,6-BPase were measured as described in [4]. Glucose was assayed using glucose oxidase [7].…”

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Effect of endotoxin on fructose 2,6-bisphosphate in isolated hepatocytes

Ceppi

Knowles

Titheradge

1990

Biochemical Society Transactions

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Comparison of the effects of [leucine]enkephalin and angiotensin on hepatic carbohydrate and cyclic nucleotide metabolism

Cited by 10 publications

References 54 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

The hyperglycemia induced by angiotensin II in rats is mediated by AT1 receptors

Effect of endotoxin on fructose 2,6-bisphosphate in isolated hepatocytes

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