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Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During the digestion of pancreatic pieces with collagenase for prepartion of isolated islets the enzymes in incubation medium (collangenolytic and/or proteolytic) can alter the secretion behavior of A- and B-cells. Insulin release after such an enzymatic attack is characterized by an enhanced basal secretion and a diminished and delayed glucose response. Overdigestion results in a decreased glucagon secretion in response to arginine, a diminished insulin content, and a decreased thiol-protein-disulfide-oxidoreductase activity of the islets. Increased albumin concentrations did not prevent the collagenase effect.
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PMID:Investigations on isolated islets of Langerhans in vitro. XIII. Experiments concerning the preparation conditions with collagenase. 17 1

The transplantable islet-cell tumor of the golden hamster has already been shown to produce hypoglycemia and hyperinsulinemia in the receptor animal. The present study demonstrates that the plasma pancreatic glucagon concentrations are significantly increased in the tumor-bearing animals but that this hyperglucagonemia is not abolished by administration of glucose or of diazoxide. It is also unresponsive to arginine administrations. In these animals, increased peripheral glucagon plasma concentrations are observed along with a reduced porto-aortic glucagon gradient. Moreover, plasma glucagon in the vena cava is usually higher than that in the aorta and a significant quantity of glucagon is found in the tumor. We conclude that glucagon release from the tumor is in fact responsible for the observed hyperglucagonemia.
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PMID:Glucagon secretion by the transplantable islet-cell tumor of the Syrian hamster. 17 26

The insulin response to oral glucose, tolbutamide, arginine, pancreozymin and cerulein was studied in a group of subjects with insuloma and a group of normal control subjects. The same parameters were studied in a small number of cases after administration of secretin and gastrin. The glucagon response (IRG) to arginine, pancreozymin and cerulein was also studied. In subjects with insulomas plasma IRI values after oral glucose, tolbutamide and pancreozymin, starting from elevated basal levels, reached high absolute levels though the increase above basal levels did not differ significantly from normal. After cerulein plasma IRI values increased in some insuloma patients but not in normal subjects. After arginine the plasma IRI increase above basal levels was significantly lower than normal in patients with insulomas. The glucagon response to arginine was normal in the patients with insulomas; these patients showed a clearcut glucagon response to cerulein and a very irregular response after pancreozymin.
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PMID:Response of islet cell tumors to enterohormones. 17 27

When glucagon release from monolayer cultures of newborn rat pancreas was measured over four hours in media containing 2.5 mM Ca++, a significant cyclic AMP-related inhibition of release was observed. This was noted whether intracellular cyclic AMP levels were raised by the addition of exogenous cyclic AMP or dibutyryl cyclic AMP, by phosphodiesterase inhibition with theophylline, or by the stimulation of adenylate cyclase with cholera toxin. The inhibition was concentration dependent for cyclic AMP and could not be reproduced by the addition of AMP, ADP or ATP. Adenosine also inhibited glucagon release while ATP was stimulatory. From time course studies it appeared that the inhibitory effects of cyclic AMP and cholera toxin were progressive after two hours of incubation. With cholera toxin an early stimulation of glucagon release was observed. The effects of cyclic AMP and cholera toxin on arginine-stimulated glucagon release were to stimulate further the glucagon release during the first hour of the incubation. Thus, the effects of raising intracellular cyclic AMP levels were biphasic in that both an early stimulation and a late inhibition of glucagon release were observed. In examining the nature of these responses a remarkable controlling role for Ca++ was uncovered: at Ca concentrations of 0.3 mM and lower no effect of cyclic AMP on glucagon release was found. With 1 mM Ca++ in the medium cyclic AMP stimulated glucagon release early (30 min) and thereafter had no further effect. In the presence of 2.5 mM Ca++ cyclic AMP did not stimulate early but did cause the delayed inhibition of release. It is concluded that the effect of cyclic AMP on glucagon release can be either stimulatory or inhibitory depending upon the Ca++ concentration of the medium and the duration of exposure to raised cyclic AMP levels.
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PMID:Stimulatory and inhibitory effects of cyclic AMP on pancreatic glucagon release from monolayer cultures and the controlling role of calcium. 18 8

Glucagon secretion and its control have been studied in perifused isolated islets of Langerhans of the rat. It was shown that a low concentration of glucose per se does not cause increased glucagon secretion, but that at low glucose concentrations the amino acid arginine stimulates a biphasic secretory response. Such amino acid stimulated glucagon secretion can be suppressed by increasing the glucose content of the perifused media from 1.67 to 5.5 or 16.7 mM; insulin secretion is also then increased. Since high concentrations of added porcine insulin (10 mU/ml) did not affect amino acid stimulated glucagon secretion at low glucose concentration, it was concluded that high concentrations of glucose and not insulin secreted in response to that glucose are probably responsible for suppression of glucagon secretion. At low concentrations of glucose, epinephrine (2.5 X 10(-7) M) also stimulated glucagon secretion. It is concluded that isolated rat islets of Langerhans can be used for the study of glucagon secretion in vitro, and that substances appearing in the blood in vivo at low glucose concentrations are probably responsible for increased glucagon secretion under conditions associated with hypoglycemia.
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PMID:Studies on glucagon secretion using isolated islets of Langerhans of the rat. 18 96

The glucagon and insulin release induced by amino acids was studied in the presence of glucose, dibutyryl cyclic AMP (dbcAMP) or theophylline on the splenic part of the pancreas of new born rats (48 to 64 hours). The results were compared to the literature data. Arginine or a mixture of the three amino acids (A.A.), arginine, lysine or alanine, stimulate glucagon secretion at 1.6 mM glucose. This stimulation is suppressed by 16.7 mM glucose. On the other hand, 16.7 mM glucose potentiates the effect of arginine or of the 3 A.A. on insulin release. At 1.6 mM glucose, theophylline potentiates the effect of 3 A.A. (10 mM each) on glucagon and insulin release : this effect reaches a maximum at 5 mM of theophylline; dbcAMP also potentiates the effect of 3 A.A. on glucagon and insulin release, and the effect of arginine, alanine or lysine on glucagon release. On the beta cell, the lack of potentiation observed between dbcAMP and arginine, lysine or alanine indicates that these A.A. interact positively when mixed together. In the presence of arginine or of the three A.A., the percentage stimulation of glucagon and insulin release depends on the dbcAMP dose and does not vary with the glucose concentration. The increase of glucagon and insulin release observed when the NaCl concentration in the incubation medium decreases cannot account for our results. Cyclic GMP (4 mM) does not modify the glucagon or insulin secretion induced by different concentrations of glucose or by the mixture of A.A. (10 mM each). The stimulating effect of acetylcholine on insulin release would not be related to the cyclic GMP molecule. In conclusion, instead of modifying the specificity of substrate, theophylline or dbcAMP accentuate it: glucose stimulates specifically the beta cell whereas 3 A.A. are more effective on the alpha2 cell than the beta cell. Cyclic AMP suppresses the glucose effect on glucagon release induced by the amino acids. Because of its interaction with glucose and amino acids, cyclic AMP seems to be a very important element in the regulation of the release of these pancreatic hormones.
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PMID:Regulation by glucose and cyclic nucleotides of the glucagon and insulin release induced by amino acids. 18 41

Endocrine functions were investigated in a case of "beta-adrenergic hyperdynamic circulatory state". This state was diagnosed by (1) typical symptoms of cardiac awareness, (2) physical findings (increments of pulse rate and blood pressure by changing positions or walking), (3) increase in cardiac output (5.25 l/min leads to 14.03 l/min) and decrease in circulatory time (10.8 sec leads to 5.5 sec) by isoproterenol infusion (0.02 mug/min/kg body weight), (4) rapid loss of symptoms and above findings by propranolol treatment (30 mg per os daily) and reappearance by discontinuing medication. The mechanism of insulin response to glucose has been a controversy as to whether the secretion is transmitted by beta-receptor or independent glucose receptor. And in this physiologic beta-adrenergic state, it was found that insulin responses in IVGTT and OGTT were within normal limit. When beta-adrenergic condition was corrected by propranolol treatment, insulin responses were shown lowered, though in the normal range. This could be reproduced by discontinuing medication. Insulin, glucagon and growth hormone secretions caused by arginine were also found normal, but during the period the patient was on propranolol therapy, all responses were decreased, within the normal range. These results do not positively support the idea that glucose receptor is linked to beta-receptor. They do not either agree with the contention that secretions of insulin, glucagon and growth hormone induced by arginine are mediated through beta-receptors.
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PMID:Endocrine function in a case of beta-adrenergic hyperdynamic circulatory state. 18 35

Basal immunoreactive glucagon was elevated in four of nine asymptomatic relatives of a patient with glucagonoma. Immunoreactive glucagon remained elevated throughout 22 to 25 hours of continuous observation. Glucagon responses to intravenous glucose and arginine or mixed meals (or both) were abnormal, whereas glucose and insulin responses were normal. Gel filtration of plasma revealed that over 85 per cent of the four relatives' immunoreactive glucagon had a molecular weight of greater than 9000 daltons whereas that of 70 per cent of the patients with glucagonoma had a molecular weight of 3500 daltons, with the remainder eluting in the area of 9000 daltons. Pancreatic angiograms and hepatic scintiscans were normal in all four relatives. The data suggest an autosomal dominant transmission of hyperglucagonemia in this family. Immunoreactive glucagon with a molecular weight of 3500 or 9000 daltons appears to be required for the development of the clinical glucagonoma syndrome.
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PMID:Familial hyperglucagonemia--an autosomal dominant disorder. 18 88

Glucose, insulin (IRI), pancreatic (IRG) and total (GLI) immunoreactive glucagon were measured in the serum of normal hamsters and of hamsters with an insulin- and glucagon-secreting, transplantable insuloma. The tumor-bearing animals were hypoglycemic, hyperinsulinemic and hyperglucagonemic. The pancreatic islets of tumor-bearing animals secreted less glucagon and insulin in response to arginine or to changes in the glucose concentration of the medium, than did the islets of control hamsters. In addition, the introduction of glucose into the gastro-intestinal tract, which caused a significant rise in the serum GLI concentration of normal hamsters, failed to do so in the tumor-bearing animals. The results suggest that the high levels of serum glucagon and insulin induced by the tumor, suppressed IRI, IRG and GLI secretion in these animals.
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PMID:Secretion of immunoreactive insulin and glucagon in hamsters bearing a transplantable insuloma. 19 57

Described here is a patient who had an islet cell carcinoma containing both glucagon (glucagonoma) and insulin (insulinoma). Complete removal of the tumor was possible. Immunoreactive glucagon (IRG) could be extracted from all parts of the tumor (approximately 50 mug./gm.) and was shown to be fully bioactive. Immunoreactive insulin (IRI) could be extracted only from one section of the tumor (approximately 30 mug./gm.). The clinical and biochemical manifestations of the disease were dermatitis, diabetes, weight loss, anemia, hypoaminoacidemia, and hyperketonemia. The diabetes was characterized by low or normal fasting blood glucose concentrations and by impaired glucose tolerance (Kg = 0.4). After complete removal of the tumor, the dermatitis cleared, the catabolic state changed into an anabolic state, blood amino acid concentrations increased, and blood ketone-body concentrations decreased. Fasting blood glucose concentrations, however, rose above 200 mg./dl., and glucose tolerance declined further (Kg = 0.15). Hourly blood sampling for 24 hours, intravenous and oral glucose tolerance tests, intravenous arginine and tolbutamide tolerance tests with serial determinations of IRG, IRI, and blood glucose were performed preoperatively and again two weeks and two months postoperatively. The results of these studies demonstrated marked abnormalities in the stimulation and suppression of glucagon and insulin release. In addition, they failed to demonstrate a glycemic effect on the chronically elevated glucagon concentrations in this patient, while identifying insulin as the dominant factor determining blood glucose homeostasis.
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PMID:An islet cell carcinoma containing glucagon and insulin. Chronic glucagon excess and glucose homeostasis. 19 71


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