Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Serum-free, hormonally defined media have been developed for optimal growth of a rat hepatoma cell line. The cells' hormonal requirements for growth are dramatically altered both qualitatively and quantitatively by whether they were plated onto tissue culture plastic or collagenous substrata. On collagenous substrata, the cells required insulin, glucagon, growth hormone, prolactin, and linoleic acid (bound to BSA), and zinc, copper, and selenium. For growth on tissue culture plastic, the cells required the above factors at higher concentrations plus several additional factors: transferrin, hydrocortisone, and triiodothyronine. To ascertain the relative influence of hormones versus substratum on the growth and differentiation of rat hepatoma cells, various parameters of growth and of liver-specific and housekeeping functions were compared in cells grown in serum-free, hormonally supplemented, or serum-supplemented medium and on either tissue culture plastic or type I collagen gels. The substratum was found to be the primary determinant of attachment and survival of the cells. Even in serum-free media, the cells showed attachment and survival efficiencies of 40-50% at low seeding densities and even higher efficiencies at high seeding densities when the cells were plated onto collagenous substrata. However, optimal attachment and survival efficiencies of the cells on collagenous substrata still required either serum or hormonal supplements. On tissue culture plastic, there was no survival of the cells at any seeding density without either serum or hormonal supplements added to the medium. A defined medium designed for cells plated on tissue culture plastic, containing increased levels of hormones plus additional factors over those in the defined medium designed for cells on collagenous substrata, was found to permit attachment and survival of the cells plated into serum-free medium and onto tissue culture plastic. Growth of the cells was influenced by both substrata and hormones. When plated onto collagen gel substrata as compared with tissue culture plastic, the cells required fewer hormones and growth factors in the serum-free, hormone-supplemented media to achieve optimal growth rates. Growth rates of the cells at low and high seeding densities were equivalent in the hormonally and serum-supplemented media as long as comparisons were made on the same substratum and the hormonally supplemented medium used was the one designed for that substratum. For a given medium, either serum or hormonally supplemented, the saturation densities were highest for tissue culture plastic as compared with collagen gels.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Regulation of growth and differentiation of a rat hepatoma cell line by the synergistic interactions of hormones and collagenous substrata. 613 87

A modification of a technique to isolate kidney tubule fragments and pancreatic acinar cells has been used to prepare a suspension of pancreatic duct fragments from rats with pancreatic lipomatosis due to pretreatment with penicillamine and a copper-free diet. This suspension is 90-95% pure almost without any acinar cell contamination. The accumulation of 3',5'-cyclic adenosine monophosphate (cAMP) in response to various gastrointestinal hormones, hormone-like substances and theophylline was studied in these isolated pancreatic duct fragments. In the absence of theophylline, secretin increased the level of cAMP in a dose-dependent manner with a maximum at 10(-6) M. With supramaximal doses the concentration of cAMP decreased. During maximal stimulation with secretin the level of cAMP was dependent on the concentration of fragments in the incubation mixture. Vasoactive intestinal peptide (VIP) also increased the formation of cAMP. However, VIP was 10 times less effective than secretin on a molar basis. The addition of various concentrations of VIP to a submaximal dose of secretin did not alter cAMP levels as compared to the levels observed with the same concentration of secretin alone. Theophylline (5 x 10(-3) and 10(-2) M) stimulated cAMP accumulation and 5 x 10(-3) M theophylline potentiated the response to secretin and VIP. Pancreozymin (20 and 99% pure), glucagon bovine pancreatic polypeptide and carbamylcholine did not effect the level of cAMP when given alone or in combination with secretin. These data lend support to the hypothesis that cAMP is the intracellular mediator of the action of secretin and VIP on the pancreatic duct cells.
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PMID:Effects of gastrointestinal hormones and carbamylcholine on cAMP accumulation in isolated pancreatic duct fragments from the rat. 624 7

A further characterization of endotoxin-induced changes in zinc metabolism provided insight into the possible mediation processes involved. Endotoxin reduced serum zinc levels while elevating zinc associated with hepatic metallothionein (Zn-MT) in control, fasted, and zinc-depleted rats. Unlike zinc, copper in the serum and that associated with metallothionein showed little response to endotoxin. In vitro translation of liver mRNA demonstrated that metallothionein mRNA levels were increased after endotoxin administration to either control or zinc-depleted rats. Cycloheximide fully blocked endotoxin-induced alterations in serum and metallothionein zinc, but actinomycin D was only partially inhibitory. Glucagon might act as the primary mediator for these actinomycin D-insensitive changes. Glucocorticoids might be responsible for the remaining alterations in zinc metabolism because dexamethasone increased 65Zn accumulation in cultured hepatocytes, whereas endotoxin did not. In endotoxin-treated rats, the kidney as well as liver showed increases in metallothionein-zinc and metallothionein-mRNA. Virtually all the effects of endotoxin were mimicked by leukocytic endogenous mediator, implying that it probably represents the initial mediator of endotoxin action on zinc metabolism.
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PMID:Mediation of endotoxin-induced changes in zinc metabolism in rats. 638 45

Rat hepatic zinc thionein levels can be modulated by a variety of external and internal stimuli. Metals, such as zinc or copper, induce levels 20 to 50 fold over controls. Catecholamines can increase levels 10 to 20 fold, while glucocorticoids, such as dexamethasone, can increase levels modestly by 2-6 fold. We have investigated the ability of additional hormones, which have receptors on hepatocytes, to modulate the levels of hepatic zinc thionein. Glucagon, angiotensin II, and Arg-vasopressin were administered intravenously and intraperitoneally, one time and three times, over an 11 hour period. Zinc thionein levels in rat liver were increased 1.7 to 5.6 fold by glucagon and 1.7 to 3.6 fold by angiotensin II, but not at all by Arg-vasopressin, as compared to appropriate controls. Glucagon and angiotensin II, when administered in vivo, can modulate zinc thionein levels in rat liver to an extent similar to glucocorticoids. Hepatic zinc thionein levels must now be recognized to be affected in vivo by metals, glucocorticoids, catecholamines, and polypeptide hormones.
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PMID:Effects of glucagon, Arg-vasopressin, and angiotensin II on rat hepatic zinc thionein levels. 651 26

Hormonally produced changes in the synthesis and secretion of the serum copper-containing protein caeruloplasmin were studied in primary cultures of rat liver parenchymal cells isolated by the collagenase-perfusion technique. A rabbit antibody directed against rat caeruloplasmin was used to immunoprecipitate labelled caeruloplasmin. Isolated liver cells synthesized and secreted caeruloplasmin over a period of 3 days. Synthesis and secretion of this protein was enhanced when cells were treated with dexamethasone. The accumulation of copper was also moderately enhanced with glucocorticoid treatment. Inclusion of adrenaline in the culture medium resulted in elevated incorporation of copper into newly synthesized caeruloplasmin as well as an increase in 64Cu-labelled caeruloplasmin in the culture medium. However, adrenaline did not seem to increase the secretion of 3H-labelled protein, despite the elevation in secreted 64Cu-caeruloplasmin. This may be due to a large increase in the intracellular pool of 64Cu caused by enhanced accumulation of this metal when adrenaline is included in the incubation medium. Enhanced copper accumulation was also seen when cells were treated with glucagon. Adrenaline-stimulated accumulation of 64Cu could be inhibited by including phenoxybenzamine, an alpha-adrenergic blocker, in the culture medium. Elevation of extracellular copper caused enhancement in the detection of labelled caeruloplasmin in the medium of cultured cells, probably owing to the ability of this metal to stabilize the protein.
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PMID:Hormonally produced changes in caeruloplasmin synthesis and secretion in primary cultured rat hepatocytes. Relationship to hepatic copper metabolism. 688 74

The bowfin, Amia calva (order Amiiformes) occupies an important position in phylogeny as a surviving representative of a group of primitive ray-finned fishes from which the present-day teleosts may have evolved. Glucagon and glucagon-like peptide (GLP) were isolated from an extract of bowfin pancreas and their primary structures determined. Bowfin glucagon shows only four amino acid substitutions compared with human glucagon, and bowfin glucagon was equipotent and equally effective as human glucagon in stimulation of glycogenolysis in dispersed hepatocytes from a teleost fish, the copper rockfish, Sebastes caurinus. In contrast, bowfin GLP shows 15 amino acid substitutions and three amino acid deletions compared with the corresponding region of human GLP-1-(7-37)-peptide. In particular, the bowfin peptide contains an N-terminal tyrosine residue rather than the N-terminal histidine residue found in all other glucagon-related peptides so far characterized. Bowfin GLP stimulated glycogenolysis in rockfish hepatocytes, but was 3-fold less effective and 23-fold less potent than human GLP-1-(7-37)-peptide. We speculate that selective mutations in the GLP domain of bowfin preproglucagon may be an adaptive response to the previously demonstrated low biological potency of bowfin insulin.
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PMID:Structure and biological activity of glucagon and glucagon-like peptide from a primitive bony fish, the bowfin (Amia calva). 824 Mar 2

Plasma membranes (1-2 mg protein) prepared from the livers of adult male rats and human organ donors were incubated with 0.6 microM [alpha-32P] guanosine triphosphate (GTP) in an adenosine triphosphate (ATP)-regenerating buffer at 37 degrees C for 1 h; during this incubation, the [32P]GTP is hydrolyzed and the nucleotide that is predominantly bound to the membranes is [32P] guanosine diphosphate (GDP). [32P]GDP release from the liver membranes was proportional to the protein concentration and increased as a function of time. At 5 mM, Ca2+, Mg2+, Mn2+, and Zn2+ maximally inhibited GDP release by 80-90%, whereas, 5 mM Cu2+ maximally stimulated the reaction by 100%. Therefore, cations were not included in the buffer used in the GDP release step. One microM Gpp(NH)p (5'-guanylylimidodiphosphate), a nonhydrolyzable analog of GTP, maximally stimulated [32P]GDP release in the liver membranes by up to 30%. Although 10 nM Gpp(NH)p had no effect on GDP release, it appeared to stabilize the hormonal effect by blocking further GDP/GTP exchange. In the rat membranes, 1-100 nM glucagon (used as a positive control) stimulated [32P]GDP release by about 17% (P < .05); similarly, 0.1-100 nM insulin stimulated [32P]GDP release by 10-13% (P < .05). In the human membranes, 10 pM to 100 nM insulin stimulated [32P]GDP release by 7-10%. In the rat membranes, 10 nM insulin stimulated [32P]GDP release by 17 and 24% at 2 and 4 min, respectively (P < .05); in the human membranes, 10 nM insulin stimulated [32P]GDP release by about 9% at 2 and 4 min.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Insulin stimulates GDP release from G proteins in the rat and human liver plasma membranes. 826 34

The effect of zinc ions on carbohydrate metabolism and intracellular Zn2+ was studied in hepatocytes from fed rats. The addition of ZnCl2 to the medium led to an almost 3-fold increase in lactate production and an increase in net glucose production of about 50%. Half-maximal rates occurred at about 40 microM ZnCl2. These effects were not seen with Mn2+, Co2+, or Ni2+ up to 80 microM, whereas Cu2+ at 80 microM and Cd2+ or Pb2+ at 8 microM exhibited similar effects as 80 microM ZnCl2. Changes in intracellular Zn2+ were followed by single cell epifluorescence using zinquin as a specific probe. Intracellular free Zn2+ in isolated hepatocytes was 1.26 +/- 0.27 microM, and the addition of ZnCl2 led to a concentration-dependent increase in epifluorescence. CdCl2 or PbCl2 at 8 microM was as potent as ZnCl2 at 20-80 microM, whereas NiCl2 at 80 microM was without effect. ZnCl2 completely abolished the inhibition of glycolysis by glucagon (cAMP). Glucagon led to a pronounced drop in cytosolic Zn2+. Both glucagon and zinc stimulated glycogenolysis by increasing the phosphorylation of glycogen phosphorylase but acted oppositely on glycolysis. Zinc overcame the inactivation of pyruvate kinase by glucagon without changing the hormone-induced protein phosphorylation. The antagonistic action of zinc and cAMP on glycolysis together with the rapid and marked decrease in free zinc concentration induced by glucagon (cAMP) may indicate an as yet unknown role of zinc as an important mediator of regulation of carbohydrate metabolism.
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PMID:Intracellular zinc movement and its effect on the carbohydrate metabolism of isolated rat hepatocytes. 856 42

A copper deficient diet is reported to reduce acinar tissue in vivo. We investigated the suitability of this method to reduce in vivo acinar tissue mass of a rat pancreas prior to transplantation of dispersed pancreatic tissue. We also studied islet function in the acinar depleted pancreas and the outcome of transplantation of islets from such pancreata. Eighty-two Wistar Furth rats were divided into two groups with 42 animals in the control group receiving regular diet, and 40 receiving copper deficient diets (Cudt) plus tetraethylene- pentamine penta-hydrochloride (TEPA) as a chelating agent. All animals in the control group and 34 (85%) in the Cudt group tolerated this diet and survived for 60 days or longer. At the end of 60 days, all experimental animals were converted to a regular diet until the pancreata were harvested for islet transplantation. Eight rats in the Cudt group, which were converted to a regular diet for 2 weeks, and 2 in the control group were randomly selected and sacrificed to study the pancreas for acinar depletion and islet morphology. An intravenous glucose tolerance test (IVGTT) in the control group (n=24) and the Cudt group (n=25) showed K-values of 1.891+/-0.7 and 1.107+/-0.47, respectively (P-ns). Histology of pancreata showed normal acinar tissue in the control group and reduction of acinar tissue mass in the Cudt group. Furthermore, immunohistochemistry for insulin, glucagon, and somatostatin showed positively staining, while amylase was negative in the Cudt group, compared with the positive stain for cells in the control group. Standard collagenase digestion of the pancreas showed islets were surrounded by scant amounts of acinar tissue in the Cudt group compared with the control group. The islet count in the control group was 523+/-126 and 611+/-52 in the Cudt group. The mean volumes of dispersed pancreatic tissue were 0.3875+/-0.14 and 0.0668+/-0.029 ml per rat in the control and Cudt groups, respectively (P<0.05). Transplantation of dispersed pancreatic tissue from the control group into the spleen of two diabetic Wistar Furth rats resulted in the death of the recipients within 24 hr. To avoid this complication, purified islets from the control group were used for transplantation. Purified islets from 5 donor pancreata from the control group and dispersed pancreatic tissue from 3 pancreata in the Cudt group were transplanted into each recipient. Islet function was seen in 75% of the rats transplanted with purified islets from the control group, and in 67% receiving dispersed pancreatic tissue from the Cudt group. Rats with sustained islet function for 30 days following islet transplantation developed diabetes following splenectomy. The islet cells were positively stained for insulin these splenectomy specimens. This study demonstrates that rats maintained on a copper deficient diet for 60 days show depletion of collagenase digested volume of whole pancreatic tissue occurred in the Cudt as compared with the control group. Transplantation of dispersed pancreatic tissue from the acinar depleted pancreas was successful in reversing diabetes. We conclude that Cudt containing TEPA depletes exocrine tissue and facilitates pancreas digestion for successful transplantation of islets into the portal system.
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PMID:In vivo depletion of pancreatic acinar tissue simplifies islet preparation for transplantation. 882 78

Oxidation of low density lipoprotein (LDL) results in changes to the lipoprotein that are potentially atherogenic. Numerous studies have shown that macrophages cultured in vitro can promote LDL oxidation via a transition metal-dependent process, yet the exact mechanisms that are responsible for macrophage-mediated LDL oxidation are not understood. One contributing mechanism may be the ability of macrophages to reduce transition metals. Reduced metals (such as Fe(II) or Cu(I)) rapidly react with lipid hydroperoxides, leading to the formation of reactive lipid radicals and conversion of the reduced metal to its oxidized form. We demonstrate here the ability of macrophages to reduce extracellular iron and copper and identify a contributing mechanism. Evidence is provided that a proportion of cell-mediated metal reduction is due to direct trans-plasma membrane electron transport. Glucagon suppressed both macrophage-mediated metal reduction and LDL oxidation. Although metal reduction was augmented when cells were provided with a substrate for thiol production, thiol export was not a strict requirement for cell-mediated metal reduction. Similarly, while the metal-dependent acceleration of LDL oxidation by macrophages was augmented by thiol production, macrophages could still promote LDL oxidation when thiol export was minimized (by substrate limitation). This study identifies a novel mechanism that may contribute to macrophage-mediated LDL oxidation and may also reveal potential new strategies for the inhibition of this process.
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PMID:Direct copper reduction by macrophages. Its role in low density lipoprotein oxidation. 905 80


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