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)

A membrane fraction enriched in parathyroid hormone (PTH)-sensitive adenylate cyclase and sodium and potassium ion-activated (Na+, K+)-ATPase was prepared from bovine kidney. Tritiated PTH binding to this membrane fraction was dependent on both hormone and membrane protein concentration. Both total and specific binding of the hormone decreased significantly after 5 to 10 min of incubation at 22 degrees. PTH binding was highly specific, being sensitive to inhibition only with active forms of unlabeled hormone (native and 1-34 PTH). Specific binding showed a pH optimum of 7.3 to 7.5. Inhibition of binding of tritiated hormone by unlabeled PTH was also highly effective at pH 6.0, but this apparently specific binding was also inhibited by adrenocorticotropic hormone, insulin, glucagon, and vasopressin. Dissociation of bound hormone was demonstrated, and an apparent dissociation constant of 4.6 X 10(-2) min-1 was obtained. Specific binding was eliminated by pretreatment of the membranes with trypsin. The concentration dependence for inhibition of binding with unlabeled PTH was identical to that for activation of adenylate cyclase in this membrane preparation, and binding was also inhibited by concentrations of calcium in the 0.5 to 2 mM range.
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PMID:Binding of tritiated bovine parathyroid hormone to plasma membranes from bovine kidney cortex. 1 29

The kinetics for inactivation of rat liver plasma membrane adenylate cyclase by iodoacetic acid and iodoacetamide has been measured in the presence and absence of glucagon. Glucagon stimulated the rate of iodoacetic acid inhibition by a factor 9f 2.3-fold and iodoacetamide inhibition by 10-fold. These results suggest that interaction of glucagon with its receptor in the membrane resulted in conformational changes which increased either the exposure or nucleophilicity of one or more sulfhydryl groups crucial for adenylate cyclase activity. Membranes were treated with radioactively labeled iodoacetamide or iodoacetic acid in the presence or absence of glucagon and run on 5 and 7.5% sodium dodecylsulfate polyacrylamide gels. These labeling experiments revealed that two membrane components were more extensively labeled in the presence of glucagon. The first component had an apparent molecular weight of 240,000 on sodium dodecyl sulfate gels and stained positive with Coomassie blue and periodate Schiff reagent. This polypeptide accounted for approximately 1.3% of the total membrane protein. The second component had an apparent molecular weight less than 10,000 and could not be correlated directly with a well defined protein band on sodium dodecyl sulfate polyacrylamide gels. The enhancement in labeling of the 240,000 molecular weight component seen in the presence of glucagon agreed very well with that predicted from the kinetics for inhibition of adenylate cyclase activity in the presence and absence of glucagon. This correlation suggests that the component selectively labeled by this technique may be an integral component of the adenylate cyclase system and that hormone-induced conformational changes may be used to selectively label components of the adenylate cyclase system in mammalian membranes.
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PMID:Exploitation of hormone-induced conformational changes to label selectively a component of rat liver plasma membranes. 16 45

The specific binding of 125I-labeled insulin, human hormone ([125I]hGH), bovine growth hormone ([125I]bGH), and ovine prolactin ([125I]oPRL) was studied in mouse liver membranes. [125I]hGH and [125I]oPRL bound to adult liver membranes. Pregnancy increased the specific binding of [125I]hGH but not that of [125I]oPRL. [125I]hGH was displaced from membranes of pregnant mice by hGH, oPRL, and bGH, but only by hGH and oPRL from liver membranes of nonpregnant mice. Significant specific binding of [125I]bGH was seen only in pregnancy. The binding of [125I]bGH to pregnant mouse liver membranes increased with increasing concentration of either membrane protein or [125I]bGH. Both the specific binding and dissociation of [125I]bGH were greatly influenced by the time and temperature of incubation. Binding of [125I]bGH was inhibited by growth hormones, including hGH and rat GH, and not by lactogenic hormones (various prolactins and human placental lactogen), ACTH, glucagon, or insulin. The inhibition of [125I]hGH binding by hGH and bGH, in the presence of excess (2 mug/ml) of PRL, was very similar to that seen with [125I]bGH. Scatchard plots of displacement dose-response curves obtained under steady state conditions of 4C were nonlinear and very similar with either [125I]bGH or [125I]hGH. This contrasted with the linear Scatchard plots obtained from displacement dose-response curves of either [125I]oPRL or [125I]hGH in the presence of excess (2 mug/ml) bGH. Termination of pregnancy, either naturally or by hysterectomy, reduced [125I]bGH specific binding to nonpregnant levels by 24 to 36 h. Estrogen administration did not increase [125I]bGH binding in hepatic membranes. Nonpregnant mice possess hepatic lactogen binding sites which are uninfluenced by pregnancy. GH specific binding sites are markedly augmented during pregnancy. The close correlation between the level of these sites and pregnancy suggests that they are regulated by a product of the fetoplacental unit.
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PMID:Characterization and modulation of growth hormone and prolactin binding in mouse liver. 17 65

We have previously shown that adipocytes from adult (between four and five months old) rats have reduced glucagon binding and glucagon-stimulated lipolytic activity when compared with cells from young (1.5 months old) animals. In the present study we measured specific [125I] glucagon binding by purified liver plasma membranes isolated from young and adult rats. When expressed on the basis of membrane protein content, 5'-nucleotidse activity, or specific [125I] insulin binding, the extend of [125I] glucagon binding by liver membranes was not influenced by aging. Furthermore, the degree of [125I] glucagon degradation was the same in both membrane preparations. These data describe a unique condition in which glucagon binding and hormone sensitivity diminish in one tissue but remain unaltered in another.
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PMID:[125I] Glucagon binding by liver membranes from young and adult rats. 20 81

The effect of chronic treatment with a long-acting glucagon preparation on liver glucagon and insulin receptors, adenylate cyclase and plasma lipids has been examined in Zucker fatty rats (fa/fa) and their lean littermates (Fa/-). Liver insulin and glucagon receptors were examined using radioreceptor assay techniques. Neither fatty nor lean rats showed any change in insulin receptors after glucagon treatment. Glucagon receptors of the fatty rats showed a 33% drop in the number of the glucagon receptors after glucagon treatment, whilst there was no such change in the lean group. Plasma membranes of the treated fatty rats and their controls bound only 50% as much insulin per mg of liver membrane protein as those of the treated lean rats and their controls. Glucagon treatment raised plasma NEFA in lean rats and reduced them in fatty ones. Plasma cholesterol levels were reduced in both groups of animals as were plasma triglycerides, though to a lesser degree in fatty than in lean animals. Glucagon treatment increased basal and stimulated adenylate cyclase activity in the lean rats and even more so in the fatty ones. The data lend no support to the concept that hypertriglyceridaemia in fatty Zucker rats is a consequence of abnormal glucagon responsiveness.
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PMID:The effect of induced hyperglucagonaemia on the Zucker fatty rat. 20 3

Specific binding of chicken and porcine insulin was demonstrated in isolated chicken hepatocytes, chicken liver plasma membranes and chicken erythrocytes. In the liver, the binding reaction was characterized by a sensitivity and an apparent affinity which were similar to those observed in rat liver and, in contrast, by a decreased number of binding sites. In chicken liver, there were about 5 times fewer binding sites per mg of membrane protein or per unit of cell surface area than in rat liver. In chicken erythrocytes, the number of insulin binding sites per cell was even lower than in chicken hepatocytes. This decreased insulin binding was not accounted for by a faster insulin degradation in chicken tissues. Glucagon binding sites also appeared to be less numerous in chicken than in rat liver, at least at low glucagon concentration; however, the decrease in maximal binding capacity in chicken liver involved insulin and not glucagon binding. That chicken cells are equipped with insulin receptors which are less numerous than in mammalian cells may explain, partly at least, the physiological state of insulin resistance observed in the chicken.
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PMID:A study of insulin binding sites in the chicken tissues. 87 89

RMI 12330 A, (N,-(cis-2-phenylcyclopentyl) azacyclotridecan-2-imine hydrochloride), has been reported to inhibit choleratoxin-induced intestinal hypersecretion, presumably via an inhibition of mucosal adenylate cyclase (ATP:pyrophosphate-lyase (cyclizing), EC 4.6.1.1). We report here that the adenylate cyclase activity of a rat liver plasma membrane preparation was inhibited by concentrations of RMI 12330 A ranging from 10 muM to 5mM. Similar effects were observed when the adenylate cyclase preparation was assayed in the presence of 10 mM NaF, 0.1 muM glucagon or 1 muM (--)-epinephrine plus 10 muM GTP. The effect of RMI 12330 A was not due to the inhibition of the regenerating system present in the incubation medium, since the effect was preserved in its absence. The inhibition brought about by RMI 12330 A was due to a decrease in the maximal velocity of the reaction; the affinity of the enzyme for the substrate remained unmodified. The inhibition was immediate and irreversible, even after several washes of the membranes previously preincubated with the drug. Complete inhibition of cyclase was obtained at a concentration of 370 nmol of RMI 12330 A per mg of membrane protein. The drug acted with a similar dose-response curve upon intact as well as detergent-dispersed cyclase preparations.
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PMID:RMI 12330 A, an inhibitor of adenylate cyclase in rat liver. 91 55

The HLB dependency for the solubilization of membrane proteins and adenylate cyclase activity from a plasma membrane-enriched fraction from rat liver has been determined. The HLB (hydrophilic/lipophilic/balance) number of a detergent is an empirical measure of its relative hydrophobicity. Detergent HLB numbers vary systematically with the length of the ethylene oxide chain for a homologous series of detergents such as the Triton X series. These detergents have a constant hydrophobic moiety, octylphenyl, and a variable polar portion, polyethoxyethanol. Basal-NaF-epinephrine-, and glucagon-stimulated adenylate cyclase activities were solubilized in the HLB range of 16.8-17.4. Solubilization was most effective in 0.01 M Tris buffers at pH 7.5 containing 1-5 mM mercaptoethanol, 1 mM MgCl2, and 0.1% Triton X-305. The detergent to membrane protein ratio used in these studies was 3:1. Criteria for solubilization included lack of sedimentation at 100,000 X g, the absence of particulate material in the supernatant when examined by electron microscopy, and inclusion of hormonally sensitive adenylate cyclase activity in Sephadex G-200 gels. The apparent molecular weight of the solubilized enzyme was approximately 200,000 in the presence of Triton X-305. The solubilized enzyme was stimulated 5-fold by NaF, 7-fold by glucagon, and 20-fold by epinephrine compared to the particulate enzyme used in this study which was stimulated 10-fold, 3.4-fold, and 4-fold by NaF, epinephrine, and glucagon, respectively. The solubilized enzyme is stable for several weeks when stored at -60 degrees C.
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PMID:The HLB dependency for detergent solubilization of hormonally sensitive adenylate cyclase. 126 11

1. 125I-labelled secretin bound rapidly and specifically to membranes from cat pancreas. Binding of labelled hormone was competitively inhibited by unlabelled secretin in the same range of concentrations that stimulated pancreatic adenylate cyclase in these membranes. The dissociation constant of the membrane binding sites for unlabelled secretin as evaluated by these displacement experiments was 4.1-10(-9) M and the number of binding sites 1.0 pmol per mg of membrane protein. 2. Studies using different concentrations of [125I]secretin (at a constant ratio of labelled to unlabelled hormone) revealed a similar value of 4-4-10(-9) M for the dissociation constant. 3. Both the association and dissociation rate constants of [125I]secretin binding were temperature sensitive; the dissociation rate constant increased more rapidly with increase in temperature. The ratio k-1/k+1 (at 22 degrees C) gave a dissociation constant of 3.7-10(-9)M which agrees closely with the figure obtained from equilibrium data. These data indicate that 125I-labelled secretin and unlabelled secretin bind to the same binding site on pancreatic membranes, with high affinity. 4. Unlabelled secretin stimulated pancreatic adenylate cyclase with an apparent Km of 8.4-10(-9) M, while [125I]secretin apparently did not stimulate the adenylate cyclase. Together with the binding data this might suggest that different portions of the secretin molecule are responsible for binding and adenylate cyclase activation. 5. Studies on the specificity of [125I]secretin binding carried out with various peptide hormones (glucagon, human gastrin, pancreozymin and caerulein) which are all inefficient in stimulating pancreatic fluid secretin, showed that these hormones have no influence on the binding of [125I]secretin. In contrast, vasoactive intestinal polypeptide, which stimulates pancreatic fluid and bicarbonate secretion, showed a competitive inhibition of secretin binding to the plasma membrane preparation.
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PMID:The interaction of secretin with pancreatic membranes. 127 8

Challenge of intact hepatocytes with one of the hormones vasopressin, angiotensin and glucagon or with the phorbol ester phorbol 12-myristate 13-acetate (PMA) led to a rapid increase in the activity of protein kinase C found in both cytosol and membrane fractions. Maximal activation by hormones occurred within 1-6 min of challenge of cells, after which activity declined. In membrane fractions protein kinase C activity return to basal levels some 15 min after exposure of cells to either angiotensin or glucagon. In cytosol fractions of cells challenged with hormones a second phase of activation ensued after about 10 min, with levels of protein kinase C activity remaining elevated above basal level 15 min afterwards. Activity changes elicited by PMA were rather different; it took about 15 min to achieve maximal activation of cytosolic protein kinase C activity. In membranes of cells challenged with PMA, an initial rapid and transient activation was followed by a sustained increase in activity occurring about 10 min after exposure of cells to this ligand. Only when hepatocytes were challenged with PMA was the translocation of protein kinase C from the cytosol to membrane fraction observed. The kinetics of PMA-induced translocation suggested that it accounted for the second phase of the increase in membrane protein kinase C activity which was unique to this ligand.
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PMID:Glucagon, vasopressin and angiotensin all elicit a rapid, transient increase in hepatocyte protein kinase C activity. 157 78


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