Gut Glucagon-like Immunoreactivity Research Articles

The Enigmatic N-Terminal Domain of Proglucagon; A Historical Perspective.

Enteroglucagon refers to the predominant peptide with glucagon-like immunoreactivity (GLI) that is released by the intestine into the circulation in response to nutrients. Development of a radioimmunoassay for glucagon revealed issues that were not apparent in applications of the insulin radioimmunoassay. The fact that some antisera raised against glucagon recognized glucagon-related peptides in extracts of both pancreas and gut whereas others recognized only components in the pancreas remained a mystery until it was realized that the “gut GLI cross-reactive” antisera were directed against an epitope in the N-terminal to central region of glucagon whereas the “pancreatic glucagon specific” antisera were directed against an epitope in the C-terminal region. Unlike the cross-reactive antisera, the glucagon specific antisera did not recognize components in which glucagon was extended from its C-terminus by additional amino acids. Initial attempts to purify enteroglucagon from porcine ileum led to the erroneous conclusion that enteroglucagon comprised 100 amino acids with an apparent molecular mass of 12,000 Da and was consequently given the name glicentin. Subsequent work established that the peptide constituted residues (1-69) of proglucagon (Mr 8128). In the 40 years since the structural characterization of glicentin, attempts to establish an unambiguous physiological function for enteroglucagon have not been successful. Unlike the oxyntomodulin domain at the C-terminus of enteroglucagon, the primary structure of the N-terminal domain (glicentin-related pancreatic peptide) has been poorly conserved among mammals. Consequently, most investigations of the bioactivity of porcine glicentin may have been carried out in inappropriate animal models. Enteroglucagon may simply represent an inactive peptide that ensures that the intestine does not release equimolar amounts of a hyperglycemic agent (glucagon) and a hypoglycemic agent (GLP-1) after ingestion of nutrients.

Characterization of response of gut GLI to fat ingestion in dogs.

Previous study from our laboratory demonstrated that an increased release of gut glucagon-like immunoreactivity (GLI) following triglyceride digestion was not observed in pancreatectomized dogs. Therefore, in order to clarify the response of gut GLI to triglyceride ingestion, experimental study was carried out in normal and pancreatectomized dogs. When butter was administered to pancreatectomized dogs in combination with pancreatic enzymes, plasma glucagon (IRG) measured by specific antiserum did not change significantly but plasma triglyceride as well as plasma total immunoreactive glucagon (total IRG) measured by nonspecific antiserum increased. Oral administration of glycerol induced no significant increase in plasma IRG but elicited a moderate increase of plasma total IRG. Gastric instillation of palmitic acid induced a remarkable rise of plasma total IRG in normal dogs, whereas plasma IRG did not reveal any changes. Oral administration of triglyceride of medium chain fatty acid, tricaprylin, did not promote any rise of plasma IRG but a slight increase of plasma total IRG. From the present experiment, it is concluded that hydrolysis of triglyceride and its metabolites are important in the release of gut GLI following fat ingestion. Among its metabolites, long chain fatty acid and glycerol promote the GLI secretion, whereas medium chain fatty acid does not.

Monounsaturated Fatty Acid Diets Improve Glycemic Tolerance through Increased Secretion of Glucagon-Like Peptide-1

Diets enriched in monounsaturated fatty acids (MUFA)s have been shown to benefit glycemic control. Furthermore, MUFAs specifically stimulate secretion of the antidiabetic hormone, Glucagon-like peptide-1 (GLP-1) in vitro. To determine whether the MUFA-induced benefit in glycemic tolerance in vivo is due to increased GLP-1 release, lean Zucker rats were pair-fed a synthetic diet containing 5% fat derived from either olive oil (OO; 74% MUFA) or coconut oil (CO; 87% saturated fatty acids; SFA) for 2 weeks. Food intake and body weight gain were similar for both groups over the feeding period. The OO group had improved glycemic tolerance compared with the CO group in both oral and duodenal glucose tolerance tests [area under curve (AUC) 121 ± 61 vs. 290 ± 24 mm·120 min, P < 0.05; and 112 ± 28 vs. 266 ± 65 mm·120 min, P < 0.05, respectively]. This was accompanied by increased secretion of gut glucagon-like immunoreactivity (gGLI; an index of GLP-1 levels) in the OO rats compared with the CO rats (402 ± 96 vs. 229 ± 33 pg/ml at t = 10 min, P < 0.05). Tissue levels of GLP-1 and plasma insulin and glucagon levels were not different between the two groups. To determine the total contribution of GLP-1 to the enhanced glycemic tolerance in OO rats, the GLP-1 receptor antagonist exendin9–39 (Ex9–39) was infused 3 min before a duodenal glucose tolerance test. Ex9–39 abolished the benefit in glycemic tolerance conferred by OO feeding (OO+Ex9–39vs. CO+Ex9–39, P = NS), and resulted in a deterioration of glycemic tolerance in the OO+Ex9–39 group when compared with the OO controls (AUC 331 ± 21 vs. 112 ± 28 mm·120 min, P < 0.05). To probe the mechanism by which the OO diet enhanced GLP-1 secretion, a GLP-1-secreting L cell line was incubated for 24 h with either 100 μm oleic acid (MUFA) or 100μ m palmitic acid (SFA) and subsequently challenged with GIP, a known stimulator of the L cell. Preexposure to oleic acid but not to palmitic acid significantly increased GIP-induced GLP-1 secretion when compared with controls (55 ± 12% vs. 34 ± 9%, P < 0.01). These results demonstrate that the benefit in glycemic tolerance obtained with MUFA diets occurs in association with increased GLP-1 secretion, through a mechanism of enhanced L cell sensitivity. These results suggest that diet therapy with MUFAs may be useful for the treatment of patients with impaired glucose tolerance and/or type 2 diabetes through increased GLP-1 secretion.

Monounsaturated fatty acid diets improve glycemic tolerance through increased secretion of glucagon-like peptide-1.

Diets enriched in monounsaturated fatty acids (MUFA)s have been shown to benefit glycemic control. Furthermore, MUFAs specifically stimulate secretion of the antidiabetic hormone, Glucagon-like peptide-1 (GLP-1) in vitro. To determine whether the MUFA-induced benefit in glycemic tolerance in vivo is due to increased GLP-1 release, lean Zucker rats were pair-fed a synthetic diet containing 5% fat derived from either olive oil (OO; 74% MUFA) or coconut oil (CO; 87% saturated fatty acids; SFA) for 2 weeks. Food intake and body weight gain were similar for both groups over the feeding period. The OO group had improved glycemic tolerance compared with the CO group in both oral and duodenal glucose tolerance tests [area under curve (AUC) 121 +/- 61 vs. 290 +/- 24 mM.120 min, P < 0.05; and 112 +/- 28 vs. 266 +/- 65 mM.120 min, P < 0.05, respectively]. This was accompanied by increased secretion of gut glucagon-like immunoreactivity (gGLI; an index of GLP-1 levels) in the OO rats compared with the CO rats (402 +/- 96 vs. 229 +/- 33 pg/ml at t = 10 min, P < 0.05). Tissue levels of GLP-1 and plasma insulin and glucagon levels were not different between the two groups. To determine the total contribution of GLP-1 to the enhanced glycemic tolerance in OO rats, the GLP-1 receptor antagonist exendin(9-39) (Ex(9-39)) was infused 3 min before a duodenal glucose tolerance test. Ex(9-39) abolished the benefit in glycemic tolerance conferred by OO feeding (OO+Ex(9-39) vs. CO+Ex(9-39), P = NS), and resulted in a deterioration of glycemic tolerance in the OO+Ex(9-39) group when compared with the OO controls (AUC 331 +/- 21 vs. 112 +/- 28 mM.120 min, P < 0.05). To probe the mechanism by which the OO diet enhanced GLP-1 secretion, a GLP-1-secreting L cell line was incubated for 24 h with either 100 microM oleic acid (MUFA) or 100 microM palmitic acid (SFA) and subsequently challenged with GIP, a known stimulator of the L cell. Preexposure to oleic acid but not to palmitic acid significantly increased GIP-induced GLP-1 secretion when compared with controls (55 +/- 12% vs. 34 +/- 9%, P < 0.01). These results demonstrate that the benefit in glycemic tolerance obtained with MUFA diets occurs in association with increased GLP-1 secretion, through a mechanism of enhanced L cell sensitivity. These results suggest that diet therapy with MUFAs may be useful for the treatment of patients with impaired glucose tolerance and/or type 2 diabetes through increased GLP-1 secretion.

Elevated content and secretion of gut GLI in VMH-lesioned rats

Gut glucagon-like immunoreactivity (GLI), a supposed intestinal growth factor in the plasma and gastrointestinal tract, and weight of the gastrointestinal tract, an intestinal growth indicator, were examined in ventromedial hypothalamic (VMH)-lesioned rats 1 week after VMH lesions. Postprandial plasma gut GLI in VMH-lesioned rats was significantly higher than that in control rats. The content of gut GLI in all gastrointestinal sections except the duodenum in VMH-lesioned rats was significantly greater than that in control rats. Gel chromatography in the lower portion of the small intestine in which GLI content was the highest of all sections revealed the same pattern in both VMH-lesioned and control rats with two peaks of similar molecular size. Weight of all gastrointestinal sections except the cecum in VMH-lesioned rats significantly increased. These results demonstrated that both gut GLI secretion and production were enhanced in VMH-lesioned rats. The elevated gut GLI release may accelerate growth of the gastrointestinal tract in these animals.

Response of gut glucagon-like immunoreactivity to hypoglycemia in dogs.

Previous studies demonstrated that insulin-induced hypoglycemia enhances glicentin secretion in piglets and prompted us to investigate the response of glucagon-like immunoreactivity (GLI) to hypoglycemia in dogs. Insulin hypoglycemia did not induce any rise of plasma total immunoreactive glucagon (IRG) measured by nonspecific antiserum to glucagon in normal or pancreatectomized dogs under anesthesia. In contrast, insulin-induced hypoglycemia clearly increased plasma total IRG in both normal and pancreatectomized dogs in a conscious state. Administration of acetylcholine resulted in an elevation of plasma total IRG, whereas epinephrine induced a slight increase in plasma total IRG. The infusion of alpha- or beta-adrenergic blockers did not affect the response of plasma total IRG to hypoglycemia, whereas atropine completely blunted the increase in plasma total IRG during insulin hypoglycemia. Similarly atropine abolished the rise of plasma total IRG during intravenous administration of 2-deoxy-D-glucose. It is concluded that hypoglycemia clearly enhances the secretion of GLI from the gut in dogs and that GLI secretion during hypoglycemia is modulated, at least in part, by the autonomic nervous system.

Effect of insulin on the response of gut glucagon-like immunoreactivity (GLI) to oral glucose and food ingestion in the goose.

Gut GLI levels were measured in the plasma of normal, totally and subtotally depancreatized geese, using an antiserum specific for avian pancreatic glucagon and another one which crossreacts with intestinal extracts. Gut GLI was determined by difference between "total" GLI and immunoreactive pancreatic glucagon (IRG). Glucose given orally or a meal rich in carbohydrates elicited an elevation in plasma gut GLI. The increment of gut GLI was greater when the pancreas was removed. The over-stimulation of gut GLI was corrected by the administration of insulin. This is the first study which reports a correlation between insulin and gut GLI secretion in birds.

Glucagon-related peptides in the rat hypothalamus.

Immunohistochemically, nerve fibers and terminals reacting with anti-N-terminal-specific but not with anti-C-terminal-specific glucagon antiserum were observed in the following rat hypothalamic regions: paraventricular nucleus, supraoptic nucleus, anterior hypothalamus, arcuate nucleus, ventromedial hypothalamic nucleus and median eminence. Few fibers and terminals were demonstrated in the lateral hypothalamic area and dorsomedial hypothalamic nucleus. Radioimmunoassay data indicated that the concentration of gut glucagon-like immunoreactivity was higher in the ventromedial nucleus than in the lateral hypothalamic area. In food-deprived conditions, this concentration increased in both these parts. This was also verified in immunostained preparations in which a marked enhancement of gut glucagon-like immunoreactivity-containing fibers and terminals was observed in many hypothalamic regions. Several immunoreactive cell bodies were found in the ventromedial and arcuate nuclei of starved rats. Both biochemical and morphological data suggest that glucagon-related peptides may act as neurotransmitters or neuromodulators in the hypothalamus and may be involved in the central regulatory mechanism related to feeding behavior and energy metabolism.

Inhibition of pentagastrin-stimulated gastric acid secretion by intraileal administration of bile and elevation of plasma concentrations of gut glucagon-like immunoreactivity in anesthetized dogs

The effects of intraileal administration of bile on gastric acid secretion stimulated by a submaximal dose of intravenous pentagastrin infusion and on plasma concentrations of gut glucagon-like immunoreactivity (gut GLI) were studied in anesthetized dogs. Gastric acid secretion was measured for a 2-h period at 15-min intervals before and after intraluminal instillation of test solutions. 100 ml of canine bladder bile diluted to 10% in saline evoked a significant inhibition (20%) of gastric acid secretion. The inhibition of gastric acid secretion was accompanied by an elevation of plasma concentration of gut GLI, whereas saline instillation (in controls) caused no responses. Although the inhibition of gastric acid secretion and the elevation of plasma gut GLI are parallel phenomena, gut GLI can be reasonably postulated as one of the candidate mediators of bile-induced inhibition of gastric acid secretion, since its structurally related peptides, pancreatic glucagon, glicentin and oxyntomodulin have been reported as inhibitors of gastric acid secretion.

Effect of glicentin-related peptides on glucagon secretion in anaesthetized dogs.

Recent studies have demonstrated that glicentin is released during nutrient ingestion. However, the biological function of glicentin remains unclear. In order to clarify the role of glicentin in the enteroinsular axis, the effect of glicentin-related peptides was investigated using in vivo local circulation of canine pancreas. Peaks I and II of gut glucagon-like immunoreactivity, partially purified from porcine intestinal extract by affinity chromatography and gel filtration, synthesized hexadecapeptide of N-terminal glicentin (1-16) and synthesized octapeptide of C-terminal glicentin (62-69) were administered for 10 min into the pancreaticoduodenal artery of canine pancreas. Blood samples were then drawn from the pancreaticoduodenal vein. The administration of peak I of glucagon-like immunoreactivity during arginine infusion in a dosage of 20 ng reduced the glucagon secretion by 42 pmol/l (p less than 0.05), whereas peak II of glucagon-like immunoreactivity (20 ng) slightly increased the plasma level of insulin, although not significantly. The administration of glicentin (1-16) in a dosage of 400 ng during saline infusion did not alter the plasma insulin level, but reduced the plasma glucagon level in the pancreaticoduodenal vein by 29 pmol/l (p less than 0.05). In addition, glicentin [62-69] in a dosage of 400 ng exerted a decrease in both the plasma insulin (40 mU/l, p less than 0.05) and glucagon level (27 pmol/l, p less than 0.05). The present study demonstrates the suppression of pancreatic glucagon release during the infusion of peak I glucagon-like immunoreactivity and N- or C-terminal glicentin-related peptide. Therefore, it is suggested that glicentin released during nutrient intake might inhibit the secretion of glucagon.

Production and characterization of N-terminally and C-terminally directed monoclonal antibodies against pancreatic glucagon

Hybridoma technology has been successfully applied to the production of monoclonal antibodies against a variety of small soluble peptides. We report herein for the first time on the development of monoclonal antibodies to pancreatic glucagon. Twenty-three stable positive hybridomas were detected by radioimmunoassay from five separate fusions and cloned by the limiting dilution method. Four selected monoclonal antibodies were all of the IgG 2a subclass type κ and bound to protein A. One monoclonal antibody (23.8B6) was shown to be directed toward the C-terminal region and another (23.6B4) toward the N-terminal to central region of the glucagon molecule. These antibodies did not cross-react with any of the other peptides tested. Two further monoclonal antibodies (23.4A1, 22.3A6) reacted with the C-terminal third of the glucagon molecule and showed a cross-reaction with the structurally related gastric inhibitory polypeptide of 0.7% and 9.1%, respectively. All but the C-terminal monoclonal antibody 23.8B6 showed a marked cross-reaction with ileal extracts. The N-terminally directed monoclonal antibody 23.6B4 was of sufficient avidity for use in the radio-immunoassay of pancreatic glucagon and gut-glucagonlike immunoreactivity in tissue extracts, being sensitive to changes of pancreatic glucagon of 2.0 fmol/tube at a final titer of culture supernatant of 1:1.4 × 105. In gel permeation chromatography of intestinal extracts, two major peaks were detectable (Kav 0.27 and 0.54). The present findings show that monoclonal antibodies provide sensitive tools for detecting pancreatic glucagon and gut-glucagonlike immunoreactivity. They will be valuable immunoreactants for the development of immunoradiometric assays as well as for large-scale immunoaffinity purification of gut-glucagonlike immunoreactivity.

Production of glucagon and gut glucagon-like immunoreactivity by a human pancreatic glucagonoma in culture

Production of glucagon and gut glucagon-like immunoreactivity by a human pancreatic glucagonoma in culture

Response of extrapancreatic immunoreactive glucagon to intraluminal nutrients in pancreatectomized dogs.

To investigate the response of extrapancreatic glucagon to intraluminal stimuli, nutrients were administered to normal and pancreatectomized dogs through a stomach tube in a fully conscious state after an overnight fast. Plasma immunoreactive glucagon was determined with antisera specific and nonspecific to glucagon and was designated as IRG and total IRG, respectively. Oral glucose load elicited a decrease in plasma IRG and a remarkable rise of plasma total IRG in a group of 6 pancreatectomized dogs, as in the control dogs. When arginine was given, both plasma IRG and total IRG significantly increased in a group of 5 pancreatectomized dogs, while only total IRG rose significantly in the normal control dogs. Butter load did not reveal any changes in plasma IRG and total IRG in a group of 5 pancreatectomized dogs, whereas only total IRG increased in the normal control dogs. It is concluded that extrapancreatic glucagon responds to intraluminal administration of nutrients, as pancreatic glucagon does. In addition, gut glucagon-like immunoreactivity increased following glucose or arginine ingestion in pancreatectomized dogs. Furthermore, the failure in response of plasma IRG and total IRG to butter load in pancreatectomized animals suggests that its intraluminal hydrolysis is important in the secretion of extrapancreatic immunoreactive glucagon.

Gastroenteropancreatic hormones in normal and gestational-diabetic pregnancy: Response to oral lipid

The effect of normal and gestational-diabetic pregnancy on the gastroenteropancreatic (GEP) hormone response to lipid ingestion was studied in 17 women, 8 normal and 9 with gestational diabetes, by determination of the plasma concentrations of gastric inhibitory polypeptide (GIP), gut glucagon-like immunoreactivity (gut GLI), insulin, glucagon, and pancreatic polypeptide (PP) following the ingestion of 67 g of triglyceride in late pregnancy and postpartum. Also, the plasma concentrations of free fatty acids (FFA), triglyceride, and glucose were determined. In both groups fasting plasma triglyceride and insulin were increased and PP was decreased. Fasting plasma glucose and gut GLI were decreased in normal pregnancy, but were unaltered in gestational-diabetic pregnancy. Fasting plasma glucagon were unaltered in normal but increased in gestational diabetic pregnancy. In both groups of women the GIP response to triglycerides was impaired in pregnancy. Postpartum, the GIP response was greater in the gestational diabetics than in normal women whereas no difference was found in pregnancy. The other hormones and metabolites responded similarly in pregnancy and postpartum and no difference between normal women and women with gestational diabetes was found. It is concluded that the GIP response to triglycerides is impaired in pregnancy.

Effects of total pancreatectomy on the secretion of gut glucagon in humans.

To determine how total pancreatectomy influences the secretion of gut glucagon in man, 15 totally pancreatectomized patients (Px), 14 distally gastrectomized patients (Gx), and 15 healthy subjects were investigated by intravenous arginine infusion test and oral glucose tolerance test. Blood glucose, plasma insulin (IRI), and C-peptide (CPR) levels were determined. Plasma immunoreactive glucagon (IRG) and total glucagon-like immunoreactivity (total GLI) were also measured. Gut glucagon-like immunoreactivity (gut GLI) was calculated to be the difference between total GLI and IRG. In the Px group, arginine infusion did not significantly alter the levels of IRI, CPR, IRG, and gut GLI. Mean basal value of gut GLI in the Px group of 356 +/- 40 pg/ml was significantly higher than 179 +/- 26 pg/ml of the healthy (p less than 0.01) and 182 +/- 24 pg/ml of Gx group (p less than 0.01). Oral glucose loading led to the highest increase of gut GLI in the Px group (p less than 0.01). Thus, extrapancreatic IRG may not be secreted into the plasma in totally pancreatectomized humans in response to arginine stimulation. Complete absence of the pancreas and the deficiency of insulin-effect may lead to a hypersecretion of gut GLI, both in the basal state and after oral glucose loading.

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.

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.

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.

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.

Plasma Insulin, Glucagon, and Gut Glucagon-like Immunoreactivity during Experimentally Induced Hyperammonemia in Rats

SummaryFed and fasted rats injected with urease showed a dramatic and sustained elevation in plasma ammonia concentrations. Plasma glucose concentrations were also elevated following urease treatment in both fed and fasted rats. The increase in plasma ammonia following urease treatment was accompanied by a significant increase in the average plasma insulin concentrations in both groups. There was no consistent effect of ammonia intoxication on plasma glucagon or gut glucagon-like immunoreactivity.