Glucagon-like Immunoreactivity Research Articles

Molecular Forms of Glucagon-Like Immunoreactivity in Porcine Intestine and Pancreas*

Glucagon-related polypeptides in porcine pancreas and intestine were analysed by gel-permeation chromatography and RIA. Three assays were employed: a nonspecific glucagon assay (R59) of 94% cross-reactivity with glicentin; a pancreatic glucagon assay (RCS5) directed against the C-terminal region of glucagon and of less than 0.01% cross-reactivity with glicentin; and a glicentin assay (R64) of less than 0.01% cross-reactivity with glucagon. For extracts of porcine pancreas all three assays gave similar molar concentrations of immunoreactivity. In porcine intestinal extracts immunoreactivity was detected in significant amounts only by the nonspecific glucagon (R59) and the glicentin (R64) assays, again in similar molar concentrations. The immunoreactivities present in pancreas and intestine were chromatographically and immunologically separable into six main peaks, peaks I, II, III, V, and VI being present in the pancreas, and peaks I, II, and IV in the intestine. The different immunoreactivities of the peaks allowed probable identities to be assigned to their main components. Apart from peak I, which consists of void-volume material that may interfere nonspecifically with the assays, the main components of the peaks can be interpreted as glicentin (in peak II) or fragments derived from glicentin. Peak III contains the N-terminal portion of glicentin (glicentin-related pancreatic peptide), peak IV probably contains glucagon with its 8 amino-acid C-terminal extension, peak V is pancreatic glucagon and peak VI contains smaller N-terminal glicentin fragments. These findings fit with the proposition that glicentin fulfills the role of proglucagon in the pancreas, and is the major component of enteroglucagon in the intestine.

Distribution and molecular forms of bombesin and glucagon-like immunoreactivities in human brain

Distribution and molecular forms of bombesin and glucagon-like immunoreactivities in human brain

Localization and characterization of glucagon-like immunoreactivity in avian retina: N. Brecha, M. Cilluffo, and T. Yamada. Center for Ulcer Research and Education, VA Wadsworth Medical Center and UCLA School of Medicine, Los Angeles, California 90073, U.S.A.

Localization and characterization of glucagon-like immunoreactivity in avian retina: N. Brecha, M. Cilluffo, and T. Yamada. Center for Ulcer Research and Education, VA Wadsworth Medical Center and UCLA School of Medicine, Los Angeles, California 90073, U.S.A.

Plasma levels of glucagon-like polypeptides in gastrectomized patients transformed from Billroth II into Billroth I.

An oral glucose tolerance test (OGTT) has been performed in a group of patients with partial gastrectomy before and after transforming the anastomosis from Billroth type II (B II) into Billroth type I (B I). Glucose tolerance was normal in both groups. The statistically significant differences in blood glucose (BG) values observed at 30 min between B I and normals and at 30, 60 and 90 min between B II and normals occur without concomitant changes in insulin (IRI) plasma levels. In the course of the test a marked rise (statistically significant from 30 to 180 min) in glucagon-like immunoreactants (GLI) plasma levels was noted in B II patients and has been attributed to the rapid intestinal transit. Otherwise, the restoration of duodenal passage induced a clear decrease of GLI levels which returned to normal values. Increased immunoreactive glucagon (IRG) plasma levels in B II group do not seem to be due to cross-reactivity with GLI. The raised BG levels occurring in B II cannot be attributed either to a reduced insulin secretion or to an increase in biologically active components of glucagon.

Glucagon-like immunoreactants in extracts of the rat hypothalamus.

Immunohistochemical studies have revealed that materials with glucagon-like immunoreactivity but not genuine glucagon are present in rat hypothalamus (RH). In contrast, both glucagon-like immunoreactants and, presumably, genuine glucagon have been detected in canine brain extracts. We report here the extraction and partial characterization of glucagon-like immunoreactants from RH. Initial extractions of whole brain were made in acid-saline (pH 2.8) in the presence of 1,000 kallikrein international units (KIU)/ml Trasylol (T) or 2 mg/ml benzamidine. Both 30K (C-terminally directed) and K4023 (centrally directed) glucagon antisera showed considerable apparent immunoreactivity, which diluted in parallel with standard porcine glucagon. Gel filtration on Sephadex G-150 demonstrated a peak of 90,000 molecular weight, which, surprisingly, reacted identically with both 30K and K4023. However, these extracts caused marked degradation of [125I]iodoglucagon despite the presence of up to 2,000 KlU/ml T or 10 mg/ml be...

Localization of carcinoids and pheochromocytomas with vein catheterization and amine determination

Selective catheterization of hepatic, intestinal and adrenal veins with blood sampling for serotonin and catecholamine determination was evaluated regarding its use in the diagnosis, location and characterization of carcinoids and pheochromocytomas. Catheterization of intestinal veins via the transhepatic route and of the adrenal veins via the femoral and caval veins was performed in 49 patients without major complications. High pressure liquid chromatography with electrochemical detection was used to quantitate norepinephrine and epinephrine in plasma and serotonin in plasma and whole blood. Serotonin in plasma was also determined by an enzymatic procedure. In 30 patients with suspected or verified carcinoid tumors concentration of serotonin in tumor-draining veins was clearly elevated in all patients but one. In this patient, who previously had been treated with temporary liver dearterialization, the serotonin concentration in the hepatic vein was within the normal range in spite of the existence of liver metastases. Hyperserotoninemia was registered in one patient without detectable carcinoid tumor cells. In three patients determination of norepinephrine and epinephrine in adrenal venous blood diagnosed a hyperplasia and tumors in the adrenal medulla. In these cases angiography and computed tomography were negative. Microscopic analyses revealed serotonin in all carcinoids and substance P-like immunoreactivity in a large percentage of these tumors. PP-like and glucagon-like immunoreactivity were observed in two endocrine pancreatic tumors. In normal adrenal medulla and in adrenal medullary tumor tissue catecholamine fluorescence and enkephalin-like immunoreactivity were demonstrated. In the two pheochromocytomas ACTH-like, somatostatin-like and calcitonin-like immunoreactivities were identified. The technique with determinations of plasma serotonin and catecholamines in combination with selective catheterization is a useful investigation for the diagnosis, location and follow-up of patients with carcinoids and pheochromocytomas.

Renal metabolism of gut glucagon-like immunoreactivity.

To examine the role of the kidney in the catabolism of gut glucagon-like immunoreactivity (GLI), we compared the plasma GLI responses of normal and nephrectomized dogs given intraduodenal glucose loads and studied the clearance of gut GLI by the isolated perfused rat kidney. Both basal and postload plasma samples were analyzed with a glucagon C-terminal specific antibody and a GLI-reacting N-terminal antibody. The GLI response was taken to be the difference between the increments seen with these two antibodies after glucose loading. Although glucose-induced GLI increments could not be detected in untreated plasma from nephrectomized dogs, chromatographed plasma revealed a significant rise in GLI-fraction II (7000--12000 daltons) in both nephrectomized and normal dogs (732 +/- 200 and 586 +/- 111 pg/ml, respectively). We also found that crystalline glucagon was cleared by the isolated closed-circuit perfused rat kidney, but gut-GLI either as crude extract or as peak I (7000--12000 daltons) was not. Our data suggest that the kidney may not play an important role in gut-GLI catabolism.

Glicentin inhibits gastric acid secretion in the rat.

Gut glucagon-like immunoreactants (GLIs) are peptides of enteric origin, which have immunoreactivity in common with pancreatic glucagon. First reported in the intestine by Unger et al.1, GLIs are concentrated in the L-cells of the lower small intestine and the colon2. The primary structure of gut GLI-1, glicentin, a highly purified form of the major component of gut GLIs3, has recently been established. Glicentin contains 69 amino acid residues, has a molecular weight (Mr) of 8,128 (ref. 4) and contains the entire glucagon sequence4,5, thus establishing it as a member of the hormone family which includes glucagon, secretin, gastric inhibitory polypeptide and vasoactive intestinal polypeptide. Until now there have been insufficient amounts of pure glicentin to test its proposed role in the intestinal phase of the body's response to a meal6, but there is evidence which suggests that, like other members of the hormone family to which it belongs, glicentin can inhibit gastric acid secretion7–9. We confirm here that glicentin inhibits pentagastrin-stimulated acid secretion in the rat.

Rectal carcinoids as tumors of the hindgut endocrine cells

The rectal mucosa is richly endowed with a constellation of amine and polypeptide hormone-producing endocrine cell types which may be identified by silver staining and immunohistochemical methods. In order to study the relationships of rectal carcinoid tumors to the normal hindgut endocrine cells, rectal carcinoids and normal rectal mucosa were compared for the presence of argentaffinity and argyrophilia and for the distribution of a battery of polypeptide hormones. Normal rectal mucosa contained frequent cells which stained for bovine pancreatic polypeptide (PP), human PP, and glucagon-like immunoreactivity (GLI. Somatostatin (SRIF) was present in a smaller proportion of rectal endocrine cells. Both argentaffin and argyrophil cells were encountered frequently in normal rectal mucosa. In the series of 13 rectal carcinoids examined, two cases were focally argentaffin-positive, while eight tumors revealed varying degrees of argyrophilia. Eight tumors contained immunoreactive bovine PP, and four of these tumors which were tested for human PP were also positively stained. SRIF was present in five cases, while GLI was identified in two tumors. Four of the tumors were multihormonal. Rectal carcinoids have a rich polypeptide hormone content which parallels that of the normal rectal mucosa. The distinctive hormonal profile and silver staining properties may prove to be of value as specific markers for carcinoid tumors of rectal or hindgut origin.

Effects of amino-acids on pancreatic hormones and gut glucagon-like immunoreactivity in the goose.

In the goose, alanine and arginine, intravenously or orally administered, act in the same way on pancreatic hormones; they both stimulate insulin and glucagon secretions. Conversely, whereas alanine treatment has no effect on plasma gut GLI, oral arginine stimulates gut GLI secretion. Since stimulation of gut GLI secretion does not occur with i.v. arginine, it may be assumed that this secretion depends on the intestinal transit of arginine and, as already described (Sitbon and Mialhe 1979), of glucose. The results, compared with studies on a similar species (duck) and on mammals, point out that i.v. infusion of alanine stimulates IRI and GLI secretions in the goose and not in the duck. In the same way, arginine i.v. infusion, contrarily to the observation made in the duck, is without effect on gut GLI secretion in the goose. Furthermore, insulin seems to be able to inhibit the alpha cell response to arginine infusion, as in mammals, whereas this is not the case in ducks.

Enteral vs. parenteral nutrition (PN): Effect on portal (P) and systemic (A) circulating levels of gastrin, glucagon like immunoreactivities (GLI) and vasoactive intestinal peptide (VIP): [formula omitted] Univ.of Cincinnati Med.Ctr., Dept.of Surg., Cincinnati, Ohio 45267 USA. Dept.of Surg.A, Hadassah Med.Ctr., Jerusalem, Israel

Enteral vs. parenteral nutrition (PN): Effect on portal (P) and systemic (A) circulating levels of gastrin, glucagon like immunoreactivities (GLI) and vasoactive intestinal peptide (VIP): [formula omitted] Univ.of Cincinnati Med.Ctr., Dept.of Surg., Cincinnati, Ohio 45267 USA. Dept.of Surg.A, Hadassah Med.Ctr., Jerusalem, Israel

Circulating immunoreactivities of gastrin, glucagon and VIP after jejuno-ileal bypass

Seven Sprague-Dawley rats (404–440 g) underwent a 90% jejuno-ileal bypass (JIB); the functional loop consisted of 1 3 ileum and 2 3 jejunum with the bypassed loop being anastamosed to the ascending colon. Seven control rats were sham-operated. After 35 days, the rats were fasted 18 hours and venous blood was collected. Immunoreactivity of gastrin, measured with an antibody binding equally to G17 and G34, was higher in the plasma of the JIB (256±55 SEM pg/ml) than control (85±9 pg/ml) rats. This agrees with recent human studies but is in conflict with results in less mature rats. VIP levels were not significantly different. Glucagon-like immunoreactivity measured with antibodies specific for the C- and N-terminal regions of the hormone, respectively, were also higher in the JIB (510±40 and 129±15 pg/ml) rats.

INFLUENCE OF INSULIN AND GLUCAGON ON SECRETION OF GROWTH HORMONE IN GROWING DUCKS (ANAS PLATYRHYNCHOS)

An inverse age-related pattern of GH secretion has been identified in immature ducks between 2 and 9 weeks of age, the plasma level of GH falling progressively from 30-40 ng/ml at 2 weeks of age to the adult level (less than 10 ng/ml) by 9 weeks of age. This decrease in GH secretion was not accompanied by any age-related changes in the concentrations of plasma immunoreactive insulin of glucagon-like immunoreactivity or in plasma glucose or free fatty acid level. In 4- to 6-week-old ducklings the intravenous infusion of insulin (2.5 or 10 mu./kg per min for 30 min) and glucagon (0.1 or 0.5 micrograms/kg per min for 30 min) induced some inhibition of GH secretion, independently of changes in blood glucose level. These results suggest that although insulin and especially glucagon have direct effects on GH secretion in the duck, maturational differences in pancreatic function are unlikely to be causally related to the decrease in GH secretion during growth.

Species difference of glucagon-like materials in the brain

Glucagon-like materials were found in the canine, porcine, bovine, rat and human brain. Both glucagon immunoreactivity measured with an antibody against the C-terminal portion of glucagon and glucagon-like immunoreactivity measured with an antibody against the N-terminal portion of glucagon were detected in the thalamus-hypothalamus, brain stem and spinal cord, but not in the cerebrum, basal ganglia, pituitary gland or cerebellum. The distribution of glucagon-like material in the brain was common in all tested mammals.

Evidence for transformation of glucagon-like immunoreactivity of gut into pancreatic glucagon in vivo.

The effect of gut glucagon-like immunoreactivity (GLI) devoid of pancreatic glucagon was studied in piglets. All glucagon-like peptides with an accessible C-terminal were removed from the gut extract by specific antibodies reacting with the C-terminal of the glucagon molecule. Endogenous secretion of pancreatic and gut glucagon was blocked by somatostatin infusion, and then the purified gut glucagon preparation was infused. The latter prevented the hypoglycemia resulting from somatostatin infusion, and increased the glucagon level detectable by C-terminal specific antibodies in the blood of the animals. This rise was significant statistically from the 30th min of GLI administration (26.7 +/- 7.2 pg/ml versus 137.0 +/- 67.0 pg/ml; P less than 0.05) and increased until the end of the infusion (90th min, 218 +/- 60 pg/ml; P less than 0.005). It has been suggested that, owing to the in vivo enzymatic degradation of the infused gut glucagon, biologically active "pancreatic" glucagon fractions are formed extracellularly.

Evidence for transformation of glucagon-like immunoreactivity of gut into pancreatic glucagon in vivo

Evidence for transformation of glucagon-like immunoreactivity of gut into pancreatic glucagon in vivo

Effect of highly purified porcine gut glucagon-like immunoreactivity (glicentin) on glucose release from isolated rat hepatocytes

We studied the effect of the highly purified put peptide glicentin on the glucose production and cyclic AMP accumulation of isolated rat hepatocytes. Glicentin at 2·10 −7 mol/1 had the same effect on glucose production as maximally effective concentrations of glucagon, but did not stimulate cyclic AMP to the same extent; furthermore, glicentin apparently had only 1/100 of the potency of glucagon on glucose production. During incubation with hepatocytes glicentin was degraded to low molecular weight fragments some of which were chromatographically very similar to fragments of glucagon. It is suggested that glicentin exerts its glucagon-like effects on hepatocytes only after degradation of glucagon-like fragments. The results also demonstrate that the coupling between cyclic AMP accumulation and glucose production depends on the nature of the stimulatory peptide.

Changes in N-terminal glucagon-like immunoreactivity and insulin during short-term gluten challenge in childhood coeliac disease.

Sixteen patients (aged 3.5-14.3 years) with normal jejunal mucosa, originally diagnosed as having coeliac disease at least 18 months before, were started on gluten challenge. The 'end point' of challenge was significant deterioration in jejunal mucosa morphologically and morphometrically. Studies carried out both before and after challenge included intestinal absorption of D-xylose and glucose, and release of insulin and N-terminal glucagon-like immunoreactivity (N-GLI). After gluten challenge, there were significant increases in plasma N-GLI at both 45 (P less than 0.05) and 120 minutes (P less than 0.03) after oral glucose. Significant reduction occurred in glucose absorption at 45 minutes (P less than 0.04), in one-hour D-xylose absorption (P less than 0.01) and fasting serum cholesterol (P less than 0.01). Plasma N-GLI showed significant negative correlations with D-xylose absorption (P less than 0.003) and serum cholesterol (P less than 0.004).

Glucagon-Like Immunoreactivity (GLI) in Blood Plasma of Partially Hepatectomized Rats

The concentration of substances with glucagon-like immunoreactivity (GLI) was determined in arterial blood plasma of rats up to 4 weeks after partial hepatectomy. 10 h following surgery a more than 18-fold increase in GLI + glucagon immunoreactivity could be observed. About 2/3 of the maximum activity seems to be of non pancreatic origin. The levels returned to normal about 22 h after surgery.

Acute hypoglycemia in man: Neural control of pancreatic islet cell function

Acute hypoglycemia is associated with stimulation of the pancreatic alpha cells and a concurrent, prolonged suppression of insulin secretion by the beta cells. The islets receive a rich autonomic innervation and may therefore be subject to control by adrenergic and cholinergic mechanisms. The role of such neuroregulation of pancreatic islets in response to hypoglycemia has been examined in normal subjects, in subjects with a preganglionic sympathectomy due to traumatic tetraplegia, and in tetraplegic subjects given atropine to induce effective dual autonomic denervation. The normal rise of plasma norepinephrine following hypoglycemia was absent in both groups of tetraplegic subjects, providing evidence of a complete sympathectomy. Blood glucose recovery was significantly impaired only in the group of tetraplegic patients given atropine. Changes in plasma C-terminal glucagon-like immunoreactivity (C-GLI) and C-peptide immunoreactivity (CPR) following hypoglycemia were commensurate with blood glucose levels and were not significantly influenced by islet denervation. These observations suggest that neuroregulation of human islet cell function in response to hypoglycemia may be of limited importance and that stimulation of glucagon secretion may occur independent of cholinergic vagal control.