Immunoreactive Glucagon Concentrations Research Articles

Splanchnic glucagon kinetics in exercising alloxan-diabetic dogs.

The purpose of this study was to define the relationship between arterial immunoreactive glucagon (IRG) and IRG that perfuses the liver via the portal vein during exercise in the diabetic state. Dogs underwent surgery >16 days before the experiment, at which time flow probes were implanted in the portal vein and the hepatic artery, and Silastic catheters were inserted in the carotid artery, portal vein, and hepatic vein for sampling. Dogs were made diabetic with alloxan injected intravenously approximately 3 wk before study (AD) or were studied in the nondiabetic state (ND). Each study consisted of a 30-min basal period and a 150-min moderate-exercise period on a treadmill. The findings from these studies indicate that the exercise-induced increment in portal vein IRG can be substantially greater in AD compared with ND, even when arterial and hepatic vein increments are not different. The larger IRG gradient from the portal vein to the systemic circulation in AD dogs is a function of a twofold greater increase in nonhepatic splanchnic IRG release and a fivefold greater hepatic fractional IRG extraction during exercise. In conclusion, during exercise, arterial IRG concentrations greatly underestimate the IRG levels to which the liver is exposed in ND, and this underestimation is considerably greater in dogs with poorly controlled diabetes.

POORLY-CONTROLLED DIABETES SELECTIVELY INCREASES THE EXERCISE-INDUCED INCREMENT IN PORTAL VEIN GLUCAGON.

1106 The purpose of this study was to define the relationship between arterial immunoreactive glucagon (IRG) and IRG that perfuses the liver via the portal vein. Dogs underwent surgery >16 days prior to the experiment at which time flow probes were implanted on the portal vein and the hepatic artery and silastic catheters were inserted in the cartotid artery, portal vein and hepatic vein for sampling. Dogs were made diabetic with alloxan injected intravenously ≈3 weeks prior to study or were studied in the nondiabetic state. Each study consisted of a 30 min basal and 150 min moderate treadmill exercise period. Basal plasma glucose in the alloxan-diabetic (AD) dogs was threefold that of normal dogs. Although arterial insulin in the AD dogs was half that of normal dogs during rest and exercise, basal arterial IRG was not different. Arterial, portal vein and hepatic vein IRG rose by 20±11, 148±54 and 43±15 pg/ml in AD dogs and by 12±5, 43±13 and 33±10 pg/ml in normal dogs from rest to 150 min of exercise. The increase in the portal vein-arterial IRG gradient from rest to 150 min of exercise was higher in AD dogs (128±37 pg/ml) compared to normal dogs (36±9 pg/ml). Estimated hepatic sinusoidal IRG concentrations increased by 118±48 pg/ml in Ad dogs and by 38±14 pg/ml in normal dogs from rest to 150 min of exercise. Fivefold greater exercise-induced increases in hepatic fractional IRG extraction in AD dogs(0.27±0.08) when compared to normal (0.05±0.03) dogs were present. These results show that 1) the exercise-induced increments in portal vein, but not arterial or hepatic vein, IRG are substantially greater in AD dogs and 2) the larger IRG concentration gradient from portal vein to systemic circuiation is due, in large part, to a fivefold greater hepatic fractional IRG extraction. In conclusion, during exercise, arterial IRG concentrations do not accurately reflect the IRG levels to which the liver is exposed in poorly-controlled diabetic dogs.

Acute effects of distal pancreatectomy on portal and peripheral blood insulin concentrations in patients undergoing total gastrectomy.

The influence of distal pancreatectomy on portal and peripheral blood immunoreactive insulin (IRI) and immunoreactive glucagon (IRG) concentrations was evaluated in patients undergoing total gastrectomy. There were 22 patients studied, 12 of whom did not undergo distal pancreatectomy (group 1), and 10 who did (group 2). In group 2, the increase in portal blood IRI concentrations after a glucose infusion of 25 g over 30 min was suppressed, and reelevation of the portal blood IRG concentration after the glucose-induced depression was inhibited compared to group 1. In contrast, the peripheral blood IRI concentration did not reflect these changes in the portal blood IRI concentration. The rise in the arterial ketone body ratio (AKBR) and the fall in the total ketone body concentration after glucose infusion were also attenuated after distal pancreatectomy in group 2. These findings suggest that distal pancreatectomy has an immediate suppressive effect on the pancreatic secretion of insulin and glucagon, and might disturb metabolism in the liver.

Cystic Pancreatic Glucagonoma in Contact with Insulinoma Found in a Hypoglycemic Patient

Cystic glucagonoma in contact with insulinoma was found in the pancreas of a 28-year-old female patient with characteristic hypoglycemic syndrome. Among six tumors in total detected in the tail of the resected pancreas, the largest solid tumor (2.5 cm in diameter) consisted mostly of insulin-containing cells with conspicuous amyloid deposition. Contiguous to this tumor, the second largest nodule, measuring 1.8 cm in diameter, showed cystic changes and consisted of glucagon-containing cells. High concentration of immunoreactive glucagon was demonstrated in the cystic fluid. In addition to the cystic changes of endocrine pancreatic tumors, simultaneous occurrence of glucagonoma in contact with insulinoma appears to be extremely rare and repeated episodes of hypoglycemia may contribute to its pathogenesis.

Umbilical Cord Immunoreactive Glucagon Concentrations: Relation to Birth Weight and Maternal Age

Article Umbilical Cord Immunoreactive Glucagon Concentrations: Relation to Birth Weight and Maternal Age was published on April 1, 1987 in the journal Journal of Pediatric Endocrinology and Metabolism (volume 2, issue 2-3).

The effect of insulin-induced hypoglycaemia on the secretion of glucagon and hepatic glucose production in pancreatectomized dogs.

The concentration of plasma glucose in insulin deprived pancreatectomized dogs was decreased from the basal 385 +/- 44 to 65 +/- 12 mg/dL by the infusion of 7 mU X kg-1 X min-1 insulin. During the infusion, the plasma concentration of immunoreactive glucagon (IRG) did not change and hepatic glucose production was decreased. This is in contrast to earlier findings in alloxan diabetic dogs in which plasma IRG decreased in hypoglycaemia. The hypothesis is put forward that, in contrast to pancreatic alpha cells in which the effect of insulin prevails, neither insulin nor a decrease in the ambient concentration of glucose exerts any effect on the secretion of glucagon from extrapancreatic alpha cells.

Glucagon release after stimulation of the lateral hypothalamic area in rats: predominant beta-adrenergic transmission and involvement of endorphin pathways.

Catheterization of the portal vein and stereotaxic implantation of electrodes in the lateral hypothalamic area (LHA) were performed in normal rats after thiopental anesthesia. Immunoreactive glucagon (IRG) and insulin (IRI), glucose, catecholamines, and beta-endorphin were monitored in portal and peripheral plasma, before and during electrical stimulation of the LHA. The influences on glucose and hormone concentrations of propranolol, phentolamine, atropine, and naloxone infusions were also investigated in similar rats. A basal portoperipheral concentration gradient was found for IRG, IRI, and catecholamines, but not for beta-endorphin. The LHA stimulation induced a significant rise in portal catecholamine, IRG, and glucose concentrations; IRI remained unchanged; the portoperipheral catecholamine gradient was augmented. These alterations were not observed after bilateral splanchnicectomy. Propranolol infusion abolished the LHA-dependent IRG and glucose rises. Naloxone reduced the IRG rise significantly. Phentolamine and atropine did not modify the LHA-induced reactions. These results suggest that the glucagon release which follows LHA electrical stimulation depends mainly on beta-adrenergic transmission by the splanchnic nerves. Opioid peptide receptors may modulate this effect.

Endocrine responses of ducks (Anas platyrhynchos) to treadmill exercise.

Variations in the plasma concentrations of immunoreactive glucagon, insulin, triiodothyronine (T3), thyroxine (T4), prolactin, and growth hormone (GH) have been determined in adult domestic ducks during 90 min of treadmill exercise (3° grade, 1.1 km/hr). Plasma glucagon and T3 concentrations were, respectively, increased (P < 0.05 in comparison with pretreatment and sedentary control levels) after 15 and 60 min of treadmill exercise and both remained elevated thereafter. The concentration of plasma glucagon progressively increased in the control birds and was higher (P < 0.05) than the pretreatment level after 60, 75, and 90 min. The concentration of plasma T4 was markedly reduced (P < 0.05) after 15 min of exercise and progressively declined throughout the period of exercise. A similar but lesser decline in the T4 concentration was also observed in nonexercised control birds. In both the exercised and control birds the plasma insulin level declined (P < 0.02) during the course of the study, although no significant difference in the insulin concentration was observed between the groups. Plasma concentrations of GH and prolactin were unaffected by treadmill exercise or by handling and blood sampling. The hormonal responses of ducks to exercise differ from those in mammalian species.

Regulation of plasma immunoreactive glucagon in obese hyperglycaemic (ob/ob) mice.

This study examines the role of glucagon in the pathogenesis of the obese hyperglycaemic (ob/ob) syndrome in mice. Plasma C-terminal immunoreactive glucagon concentrations were measured in fed and fasted ob/ob mice at different ages between 5-40 weeks, and in 20-week-old mice after the administration of established stimulators and inhibitors of glucagon secretion. Plasma glucagon concentrations were inappropriately raised irrespective of age, nutritional status and the accompanying prominent changes in plasma glucose and insulin concentrations. Glucose suppressed plasma glucagon in the fed but not the fasted state, suggesting a dependence on the marked hyperinsulinaemia associated with feeding. Administration of 0.25 units insulin/kg to fasted mice failed to affect plasma glucagon and glucose concentrations. Increasing the dose to 100 units/kg restored the normal suppressive actions of insulin. Fasted mice showed an exaggerated glucagon response to arginine but not to the parasympathomimetic agent pilocarpine. Fed mice displayed normal plasma glucagon responses to the sympathomimetic agents noradrenaline and adrenaline. Administration of insulin antiserum or 2-deoxy-D-glucose raised plasma glucagon concentrations of fed mice. Contrary to the lack of suppression by glucose in the fasted state, heparin-induced increase in free fatty acids reduced plasma glucagon concentrations. This study demonstrates inappropriate hyperglucagonaemia and defective A-cell function in ob/ob mice. The extent of the abnormality is exacerbated by fasting and appears to result from insensitivity of the A-cell to the normal suppressive action of insulin.

Different endocrinological properties, growth rate and sensitivity to chemotherapy of aplastic mammary carcinoma in normo- and hypoglycemic phase of tumor growth

An aplastic mammary carcinoma (AMC) grew slower in hypoglycemic mice (caused by fasting or by daily insulin injections) and in hyperglycemic mice (caused by alloxan or streptozotocin, or by daily injections of glucose) than in normoglycemic mice. The tumor was able to adapt to the unfavourable conditions of the diabetes; cells, when transplanted from diabetic donors into diabetic recipients, secreted immunoreactive insulin (IRI) and immunoreactive glucagon (IRG), which are deficient in the diabetic hosts. In the terminal (hypoglycemic) phase of tumor growth, the concentrations of glucose, IRI and IRG decreased. The immunological reactivity of the host animals was reduced in the hypoglycemic terminal phase. The tumor cells taken from hosts in this phase behaved differently from the cells taken in the normoglycemic phase. The "hypoglycemic" cells grew more slowly in healthy mice; the intensity of their DNA synthesis was diminished, their response to antitumor therapy was weaker. Furthermore, it was necessary to transplant more of these cells to obtain tumors in all recipients, and they lost their ability to adapt to diabetic conditions (i.e. secreted neither IRI nor IRG). Hypoglycemia was apparently the immediate cause of death in mice with AMC. Injections of glucose or glucagon into mice with AMC eliminated the hypoglycemia temporarily and postponed the death by 4 days. Mice treated with glucagon and with chemotherapy or immunotherapy survived 6-9 days longer than mice treated with chemo- or immunotherapy alone. Some of these differences between the end-stage and the progressively growing tumors could be explained in terms of tumor cell kinetics but some could be attributed to metabolic conditions of the host caused in part by the tumor.

Insulin and glucagon responses in plasma to intraportal infusions of propionate and butyrate in sheep ( Ovis aries)

1. 1. The effects of infusions into the hepatic portal vein of propionate and butyrate at dosages approximating absorption rates on concentrations of glucose, insulin and glucagon were determined in sheep. 2. 2. Immunoreactive insulin in plasma increased significantly ( P < 0.05) during infusion of propionate and butyrate. 3. 3. Concentrations of immunoreactive glucagon in plasma did not change significantly during propionate administration but increased during butyrate administration.

Long-term effect of pancreas transplantation on diabetic hyperglucagonemia.

Pancreas isotransplantation was performed on streptozotocin-diabetic Wistar rats. To study the influence of the graft on diabetic hyperglucagonemia, immunoreactive glucagon (IRG) and its response to alanine (peak IRG) were determined in peripheral blood at intervals for up to 8 months after the transplantation. Concentrations of IRG and immunoreactive insulin (IRI) in effluent blood from host pancreas (portal vein) and graft (caval vein) were measured 4 months after the transplantation to estimate the hormone release from both organs. Following transplantation, caval IRI increased sixfold. Portal IRI increased 180% and reached 65% of the concentration observed in control rats. Peripheral basal and peak IRG were initially restored to normal, but were later increased to levels equal to those of diabetic rats. Also portal and caval IRG concentrations were similar in recipients and diabetic rats. The results show that relatively small amounts of glucagon are released from the graft, and that the exaggerated glucagon release from the host pancreas is only transiently normalized following pancreas transplantation.

Glucagon radioimmunoassay with use of antiserum to glucagon C-terminal fragment.

In this pancreatic-glucagon-specific radioimmunoassay we used C-terminal-region-specific antiserum. OAL-123, produced against a 19-29 C-terminal fragment of porcine glucagon. On measurement of pooled plasma the ranges for intra- and inter-assay coefficients of variation were 4.8-8.1% and 7.5-10.7%, respectively. The concentration of immunoreactive glucagon in plasma of healthy subjects, as measured with the OAL-123 assay system, was 87.9 (SD 23.8) ng/L. Measurement of the same plasma samples with the 30K assay system (30K being an antiserum highly specific for pancreatic glucagon) showed a comparable value, 86.2 (SD 26.3) ng/L. We followed changes in human and dog plasma immunoreactive glucagon concentrations on arginine infusion and after glucose load, using the OAL-123 and the 30K assay systems, with identical results. Combining other results of comparative immunochemical characterization of the OAL-123 and 30K assay systems, we confirmed that the antisera raised against the C-terminal fragment of glucagon can be used in radioimmunoassay of pancreatic glucagon.

Immunoreactive glucagon in nondiabetic and diabetic Macaca nigra.

The primary form of immunoreactive glucagon (IRG) in Macaca nigra has been identified as pancreatic, alpha-cell-size glucagon (IRG3500), with a molecular weight of about 3500. Assays with 30K and K-964 glucagon antibodies gave virtually identical results. Column chromatography of plasma on Bio-Gel P-30 indicated ony minimal amounts of high-molecular-weight IRG. Levels of IRG decrease during a glucose infusion, a response expected of IRG3500. IRG concentrations apparently greater than human values appear to be characteristic of nonhuman primates. Nondiabetic Macaca nigra average 641 pg of IRG3500/ml. Borderline diabetic monkeys with moderately increased glucose and impaired glucose clearance average 2,938 pg/ml. Diabetic monkeys with hyperglycemia and diminished glucose clearance have 375 pg of IRG3500/ml. Changes in IRG3500 are related to a lesion in the islets of Langerhans.

Radioimmunoassay of extracted glucagon compared with three non-extraction assays

Radioimmunoassay of glucagon was performed with three different antisera, i.e. E7, 30K and 4305, all directed against the carboxyl-terminal region of glucagon and thus avoiding co-determination of glucagon-like polypeptides from the gut. Plasma samples from five healthy people subjected to various A-cell stimulation and suppression tests were used and immunoreactive glucagon assessed with the three antisera. Aliquots from all plasma samples were also extracted with acetone and glucagon re-assessed with antiserum E7. Even though all four baseline glucagon concentrations obtained were different, the glucagon profiles were comparable after superimposing the baselines. The differences in baseline concentrations of immunoreactive glucagon seem due to the interference of “big plasma glucagon”, a still unidentified factor in the E7 and 30K assays that can be precipitated by acetone. Since acetone extraction yielded the lowest baselines without altering the glucagon profiles, it is suggested that the baseline glucagon concentrations of acetone-extracted plasma reflect the physiological level of the biologically active hormone. Using antiserum E7, our own antiserum, the normal range of glucagon values in acetone-extracted plasma samples from 22 healthy, fasting people of both sexes was 42 ± 16 ng/l (mean ± 2 S.D.). These values agree well with those obtained by other assay techniques.

Adrenergic Modulation of Pancreatic Hormone Secretion in Utero: Studies in Fetal Sheep

To assess the functional maturity of adrenergic modulation of plasma concentration of glucose, as well as immunoreactive glucagon (IRG) and immunoreactive insulin (IRI) secretion in utero, adrenergic agonists with or without beta (propranolol) or alpha (phentolamine) antagonists were infused to the chronically catheterized sheep fetus (n = 35) late in the third trimester. Mean +/- S.E. days at study was 129.5 +/- 1.5; term is 150 days. In 9 separate studies at gestational age 129 +/- 1 days, the infusion of saline for 3 hr was not associated with significant changes in the basal levels of glucose, IRG, or IRI. With epinephrine, 6 microgram/min (n = 6) glucose rose from 16.7 +/- 3.6 to 41.9 +/- 9.7 mg/dl, IRG rose from 75 +/- 8 to 219 +/- 45 pg/ml, and IRI fell from 22.6 +/- 1.7 to 12.7 +/- 3.5 microunits/ml (P less than 0.05 for each). Propranolol alone (n = 4) did not alter basal glucose or IRG but significantly suppressed IRI. Propranolol did, however, markedly attentuate the rise in glucose and IRG while exaggerating the fall in IRI during epinephrine infusion. Qualitatively similar but smaller responses were obtained with epinephrine, 0.4 microgram/min (n = 10). Similarly, elevation of glucose and suppression of IRI was obtained with norepinephrine, 2 microgram/min (n = 5), but IRG levels did not rise significantly. Alpha-Adrenergic blockade alone augmented IRI from 18 +/- 3 to 38 +/- 5 microunits/ml without affecting glucose or IRG concentrations; during alpha blockade, norepinephrine infusion failed to induce the rise in glucose, IRG remained unchanged, and IRI remained elevated (n = 5). 2-Deoxy-D-glucose, 200 mg IV over 30 min, did not affect glucose, IRG, or IRI (n = 5). Thus, appropriate adrenergic modulation of plasma concentrations of glucose, and of IRG and IRI secretion is established in the third trimester.

Circulating immunoreactive glucagon concentrations in aging obese-hyperglycaemic (ob/ob) mice [proceedings

Circulating immunoreactive glucagon concentrations in aging obese-hyperglycaemic (ob/ob) mice [proceedings

Rates of removal of exogenous and endogenous glucagon from the plasma of sheep in vivo.

The removal of exogenous and endogenous glucagon from plasma was determined in vivo in sheep weighing 53 +/- 1 (mean +/- s.e.) kg. Porcine glucagon was infused intravenously for 90 min. The metabolic clearance rates (MCR) were determined from plateau immunoreactive glucagon (IRG) concentrations in plasma and infusion rates of glucagon. The mean clearance rate (+/0 s.e.) was 16.7 +/- 1.6 litres per hour (n = 20). Upon termination of the infusion, the decrease in IRG concentrations in plasma was determined. Least-squares regression analysis of non-linear functions indicated the data fit a two-component exponential function. The time constant for the rapid component of the plasma IRG disappearance function was -0.32 +/- 0.04 min-1 (mean +/- s.e.). The time constant for the slow component was -0.22 +/- 0.008 min-1. The rate of removal of endogenous glucagon was estimated during the infusion of somatostatin when glucagon secretion was inhibited. The time constants (mean +/. s.e., n = 8) for the decrease in IRG during somatostatin infusion were -0.42 +/- 0.08 and -0.003 +/- 0.002 min-1 for fast and slow components, respectively. The time constants for the rapid components of exogenous and endogenous glucagon were not significantly different. This suggests that endogenous and exogenous glucagon are similarly removed from plasma.

Studies on plasma glucagon concentration in maturity-onset diabetics with autonomic neuropathy.

The mean fasting plasma immunoreactive glucagon (IRG) concentration in 25 non-insulin-dependent, maturity-onset diabetics (MODs) was 15.4 ± 3.1 pmol/L, which was not significantly different from the 16.8 ± 2.4 pmol/L in 17 normal controls of similar age. However, in seven MODs with autonomic neuropathy (AN) the mean fasting IRG concentration of 44.7 ± 4.4 was significantly greater than the 17.4 ±1.3 pmol/L in 18 MODs without neuropathy and compared with controls. We, therefore, investigated IRG concentrations in five age-matched, non-insulin-dependent MODs with AN and five without it. Plasma IRG concentrations were measured in the basal state on three separate occasions and in response to insulin and to a mixed meal. Fasting or basal IRG concentrations were measured in the morning with and without a preceding 12-h insulin infusion to determine the effects of reduction in fasting plasma glucose concentrations and after 12 h of nasogastric aspiration to exclude continued stimulation caused by delayed gastric emptying. In the select group of Subjects the mean basal plasma IRG concentration was raised above the normal in diabetics with AN (49.4 ± 5.1) and was 16.2 ± 2.1 in diabetics without AN, which was within normal limits. Neither 12 h of insulin infusion (0.5–0.8 U/h) nor 12 h of nasogastric aspiration altered basal IRG concentrations in either group. The maximum incremental IRG response to acute insulin administration (0.2 U/kg) in diabetics with AN was 6.8 ± 3.9, which was significantly impaired compared with 24.9 ± 4.8 in nine MODs without AN and with 26.3 ± 6.7 in five normal controls. The maximum increment in IRG response to acute insulin administration in diabetics with AN rose significantly to 32.8 ± 12.9 after 12 h of insulin infusion. Although the maximum IRG responses to a mixed meal were higher in both diabetic groups than in the normal controls, there was a delayed initial rise and persistent elevation in diabetics with AN. We suggest that (1) basal IRG concentrations may be dependent on the integrity of the autonomic nervous system in MODs; (2) MODs without AN seem to have a normal response to insulin-induced hypoglycemia, whereas in MODs with AN the response is impaired and can be corrected by an adequate degree of both insulinization and reduction in fasting blood glucose concentration; and (3) the maximum IRG response to a mixed meal is exaggerated in all MODs and is not dependent on the integrity of the autonomic nervous system, although the pattern of response may be altered in the presence Of AN.

Induction of Glucagon Synthesis in Diabetic CBA Mice Bearing Mammary Aplastic Carcinomas

Passaging of the mammary aplastic carcinoma several times in diabetic CBA mice induced an extrapancreatic secretion of glucagon. Consequently, the concentration of immunoreactive glucagon was higher in plasma and the tumor tissue extract. After the injection of alloxan, attempts to reduce the level of this hormone in the diabetic mice were unsuccessful. The tumor cells could have been responsible for the secretion of glucagon.