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)

Receptor binding assays demonstrate that bovine parathyroid hormone (PTH) and human PTH(1-34) can displace [125I]iodoglucagon from binding to its receptor in rat liver plasma membranes. The displacement of [125I]iodoglucagon requires several thousand-fold more bovine PTH or human PTH(1-34) than glucagon. However, the PTH peptides are more effective than secretin, which up to a concentration of 10(-5) M exhibits no ability to displace [125I]iodoglucagon. The greater potency of PTH compared with secretin occurs despite the fact that secretin shows a great deal of sequence homology with glucagon while PTH shows none. We demonstrate by circular dichroism that in the presence of 3 mM SDS glucagon and hPTH(1-34) have similar secondary structure contents, while secretin is more helical. Our results suggest that receptors can recognize gross conformational features of a peptide hormone in addition to interacting with a specific amino acid sequence. The ability of PTH to interact with glucagon receptors can be modulated by incorporation of charged amphiphiles into the plasma membrane. Negatively charged taurodeoxycholic acid increases the binding of the more cationic PTH while positively charged myristyltrimethylammonium bromide decreases this interaction. These effects demonstrate that receptor specificity can be modulated by its lipid environment and that electrostatic interactions between the hormone and the membrane surface can contribute to receptor binding.
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PMID:Conformational determinants in receptor recognition of peptide hormones: interaction of parathyroid hormone with the glucagon receptor. 303 Aug 52

Hepatocytes were isolated by application of the two-step collagenase perfusion technique to pieces of human liver. Hepatocytes were cultivated in serum-free medium or 10% fetal calf serum medium supplemented with insulin, glucagon and dexamethasone. The cells were kept in culture for up to 16 days and 75% of the medium was regularly changed. Fibronectin in culture medium was detected by means of an ELISA with an assay range of 2.2-560 micrograms/l. The interassay imprecision was 6.3% at 500 micrograms/l and 14.3% at 10 micrograms/l. Significant amounts of fibronectin were detected in all cultures. During culture, fibronectin accumulated in the medium and the quantity secreted by hepatocytes by far exceeded the amounts of fibronectin associated with hepatocytes prior to cultivation. Maximum secretion rate by 10(6) hepatocytes was 167.5 +/- 73.3 ng fibronectin (mean +/- SEM, n = 3) in 24 h. When analysed by means of SDS-PAGE and immunoblotting the fibronectin isolated from hepatocyte culture medium and cell lysate co-migrated with fibronectin obtained from plasma. Our data show, for the first time, that human hepatocytes synthesize and secrete fibronectin, and it is suggested that the human liver is an important source of plasma fibronectin.
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PMID:Human hepatocytes in culture synthesize and secrete fibronectin. 320 Nov 2

A proteinase from the venom of Vipera lebetina was purified by chromatography on Sephadex G-100 and CM-cellulose. The purified proteinase was homogeneous on SDS-polyacrylamide gel electrophoresis and consisted of a single chain with molecular weight of 37,000 +/- 1500. The isoelectric point of the proteinase was over 10. The enzyme was active on casein but not on esters and amides of arginine. It split the oxidized insulin B-chain at the peptide bonds of Tyr16-Leu17, Phe24-Phe25 and Phe25-Tyr26, and glucagon at the bonds Tyr10-Ser11, Leu14-Asp15 and Leu26-Met27. The enzyme was inhibited by DFP and PMSF, and partially by soybean trypsin inhibitor, but not with EDTA.
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PMID:Purification and properties of a proteinase from Vipera lebetina (snake) venom. 330 28

Intravenous injection of high doses of bacterial derived growth hormone (1 and 2 mg Somatonorm) did not affect the plasma levels of glucagon, insulin and free fatty acids in fasted and fed rabbits. On the other hand, 1 and 2 mg human extracted growth hormone (Crescormon) had stimulatory effects on plasma levels of glucagon, insulin and free fatty acids. These results indicate that the observed stimulatory effects in the rabbits were not due to the growth hormone molecule itself. It was shown by gel filtration and SDS electrophoresis that Crescormon contained constituents that were not present in Somatonorm. The differences in the observed metabolic effects of bacterial derived and pituitary growth hormone preparations in the rabbits could possibly be attributed to a human pituitary lipid-mobilizing factor LMF.
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PMID:Different acute in vivo effects of bacterial derived and pituitary growth hormone preparations on plasma levels of glucagon, insulin and free fatty acids in rabbits. 388 38

Ostrich serum albumin (OsSA) was purified by a combination of heat fractionation and polyethylene glycol precipitation. Equilibrium centrifugation revealed a relative molecular mass of 71,666 for the purified monomer, whereas the presence of a dimeric form was confirmed by means of PAGE and SDS-PAGE analysis. Compared to other species, relatively high levels of proline, glycine, isoleucine and histidine together with lowered amounts of half cystine, phenylalanine and arginine were observed in OsSA. A single N-terminal aspartic acid was identified. Isolated chicken adipocytes revealed a significantly lower in vitro lipolytic responsiveness towards added glucagon when OsSA replaced bovine serum albumin (BSA) in the medium (Km = 6.359 and 1.135 nM, Vm = 36.70 and 46.72 nmol/hr/micrograms adipocyte DNA for OsSA and BSA respectively).
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PMID:The isolation and characterization of serum albumin from the ostrich (Struthio camelus). 409 40

The hepatic glucagon receptor was covalently labeled with [125I-Tyr10]-monoiodoglucagon by use of the heterobifunctional crosslinker hydroxysuccinimidyl-p-azidobenzoate and analyzed by SDS-gel electrophoresis. The autoradiogram of the gel showed one band at Mr = 63,000 that was sensitive to excess unlabeled glucagon and GTP. The labeled receptor was solubilized with Lubrol-PX and the hydrodynamic characteristics of the receptor were determined. The molecular parameters of the solubilized receptor are S20,w = 4.3 +/- 0.1, Stokes radius = 6.3 +/- 0.1 nm, frictional coefficient f/f degrees = 1.8 and a calculated Mr = 119,000. Incubation of liver membranes at 32 degrees for 15 min prior to the addition of [125I-Tyr10] permitted us to identify the high molecular weight form (Mr approximately equal to 113,000) by direct SDS-gel electrophoretic analysis. Limited elastase treatment of the hormone-occupied receptor results in the appearance of a Mr = 33,000 fragment, that retains guanine nucleotide sensitivity. Elastase treatment of vacant receptors results in a Mr = 24,000 fragment that binds hormone in a GTP-sensitive manner. The Mr = 24,000 fragment is contained within the Mr = 33,000 fragment. The Mr = 63,000 receptor upon treatment with endo-beta-N-acetylglucosamine F for 4 h yields four fragments of apparent Mr = 61,000, 56,000, 51,000, and 45,000; 24 h treatment results in the accumulation of the last two fragments. Neither Mr = 33,000 and 24,000 fragment appear to be substrates for endo-beta-N-acetylglucosaminidase F. These data allow us to conclude that the hepatic glucagon receptor in the membrane is a dimer of approximately 60,000 dalton hormone binding subunit which is a glycoprotein containing at least four N-linked glycans accounting for 18,000 daltons of its mass. Both the hormone binding function and the capacity for the interaction with the stimulatory regulator of adenylyl cyclase are contained within a fragment of only approximately 21,000 daltons that does not contain any N-linked glycans.
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PMID:Characterization of the hepatic glucagon receptor. 609 55

Methods have been developed for the preparation of suspensions of viable rat pancreatic islet cells and their analysis and sorting in the fluorescence-activated cell sorter (FACS III or IV). Histograms of cell number versus light scattering in a near forward angle (1-15 degrees) demonstrated that viable islet cells produce a broad peak that is distinctly separated from the peaks generated by exocrine cells, erythrocytes, and nonviable cells. Electron microscopic examination and radioimmunoassay of hormone content in fractions collected across the peak showed that glucagon-containing (A) cells scatter less intensely and are concentrated within the left side of the islet cell peak, while somatostatin-containing (D) cells are localized to the far right side, indicating a higher intrinsic light scattering property of the D-cells. The more abundant insulin-containing (B) cells define the center of the islet cell peak. Sodium dodecyl sulfate slab gel electrophoresis and radioautography of 35S-methionine labeled cellular proteins confirmed that sorted cells are viable. Cells from the far left region contained increased amounts of labeled 18 Kd proglucagon and its 13-Kd and 10-Kd conversion intermediates, while cells from the right side were relatively enriched in labeled 12.4 Kd prosomatostatin. These results demonstrate that intrinsic light scattering alone can be used to prepare A- or D-cell enriched fractions from islets for biochemical analysis.
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PMID:Sorting of pancreatic islet cell subpopulations by light scattering using a fluorescence-activated cell sorter. 613 19

Administration of isopropanol (1 ml/kg body weight) via the ip route significantly depressed the serum zinc concentration within 8 hr. A maximal increase in hepatic metallothionein was observed 16 hr after isopropanol. By 48 hr after treatment metallothionein levels in liver had returned to basal levels. The extent of metallothionein induction was comparable with that observed after ip administration of zinc. Plasma glucagon concentrations were significantly elevated 4 hr after isopropanol treatment. Adrenalectomy did not prevent the isopropanol-induced changes in serum zinc or hepatic metallothionein. This suggests a nonadrenal mechanism is responsible for the observed changes. To evaluate changes in metallothionein mRNA levels in liver, in vitro translation with the wheat germ system was used to evaluate translational activity. Analysis of the labeled metallothionein produced in vitro employed both covalent chromatography as well as SDS-polyacrylamide gel electrophoresis of carboxymethylated translation products. These methods suggested the maximum metallothionein mRNA level in total RNA extract occurred about 8 hr after administration of isopropanol. Similarly, when metallothionein mRNA levels were quantitated using dot blot hybridization to [32P]cDNA for mouse metallothionein I, maximum metallothionein mRNA appeared 8 hr after isopropanol administration. The overall response of these parameters in rats suggest that isopropanol administration leads to an inflammatory-like response that, with respect to zinc metabolism, has elements which are independent of the adrenal gland, but involve transcriptional regulation of the metallothionein gene in liver.
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PMID:Changes in rat liver metallothionein and metallothionein mRNA induced by isopropanol. 614 22

Reuber hepatoma H-35 was found to retain the activity of carbamoyl-phosphate synthetase I. The content of this enzyme in H-35 grown in Eagle's minimal essential medium was about half that in rat liver. The enzyme from H-35 was the same as that from rat liver in molecular weight estimated by SDS-polyacrylamide gel electrophoresis, specific enzyme activity, kinetic parameters for ATP and N-acetyl-L-glutamate, and immunological crossreactivity. The enzyme in H-35 was induced by dexamethasone (1.4-fold) but not by glucagon or dibutyryl cAMP. Incorporation of [35S] methionine into the enzyme indicated that the effect of dexamethasone was due to increased synthesis of the enzyme protein (2.1-fold). By labeling with [35S]methionine, the precursor and the mature forms of carbamoyl-phosphate synthetase I were observed in the post-mitochondrial and mitochondrial fractions, respectively. By chasing the labeled cells with unlabeled methionine and cycloheximide, it was observed that the rate of translocation of the precursor into mitochondria is not affected by dexamethasone.
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PMID:Induction of carbamoyl-phosphate synthetase I in Reuber hepatoma H-35 by dexamethasone. 630 26

Specific labeling of liver plasma membrane glucagon receptors has been achieved by the photoincorporation of a 125I-labeled photoderivative of glucagon, NE-4-azidophenylamidinoglucagon. Identification of glucagon receptors was facilitated by irradiating membranes in the presence of excess unlabeled glucagon. Isoelectric focusing of radioiodinated membrane proteins revealed one major band of glucagon displaceable material which had an isoelectric point of 5.85. When this material was isolated and run on SDS-polyacrylamide gels a major labeled band of Mr55000 was obtained which had properties consistent with those of the glucagon receptor. These studies indicate that a purification of the glucagon receptor of greater than 700-fold can be attained through the use of isoelectric focusing and SDS-polyacrylamide electrophoresis.
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PMID:Partial purification and characterization of the glucagon receptor. 630 43


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