Plasma Immunoreactive Glucagon Research Articles

Diabetic control after total pancreatectomy

Historically, Rockey [1] demonstrated the feasibility of total pancreatectomy on a patient with pancreatic carcinoma in 1943 even if at autopsy, 1 g of pancreatic tissue adjacent to the duodenum was found. Thus, the procedure performed by Priestley et al. [2] in 1944 was considered as the first true total pancreatectomy. For many years, the use of total pancreatectomy was limited in surgical practice, but in the last 25 years, thanks to highly sensitive imaging techniques, the operability of many pancreatic diseases has increased and pancreatic resection has become more common as the operative mortality risk has fallen to less than 2%. Removal of the pancreas is often associated with a glucose intolerance called ‘pancreatogenic diabetes’; most of the studies in this field have emphasised the difficulties in glucose conanalysed after discontinuing insulin infusion, and the plasma clearance rate of insulin is significantly higher in patients with pancreatogenic diabetes than in those with type I diabetes. Thus, an up-regulation of peripheral insulin receptors in response to insulin deficiency occurs, rendering these patients uniquely sensitive to hormone replacement. Glucose intolerance after pancreatectomy may not be due to insulin deficiency alone; the reduction in beta-cell mass after an 80% proximal pancreatectomy in dogs resulted in lower peripheral insulin levels and altered glucose disappearance after glucose challenge [9]. In the altered glucose metabolism of pancreatectomised subjects, an important role is also played by glucagon deficiency [10]. After total pancreatectomy in ducks, glucagon levels are trol, considering the apancreatic patients as ‘brittle diabetics’ [3–5]. The metabolic control of apancreatic patients is rather complex because the pancreas secretes most of the hormones involved in glycaemic homeokinesis such as insulin, glucagon and pancreatic polypeptide (PP); furthermore, other gut hormones are involved in this control. The insulinsecreting beta cells are distributed evenly throughout the pancreas, whereas glucagon cells and PP cells are localised reduced to 45% of the preoperative level immediately following the procedure [11]. Controversy persists, however, over whether total pancreatectomy removes all sources of glucagon production. Some authors have reported no detectable circulating plasma immunoreactive glucagon after total pancreatectomy in humans [10], whereas others have detected varying amounts of the hormone in the plasma of pancreatectomised patients [12]. Although there may be enteric sources of glucagon production in humans after total selectively in the tail and the head of the pancreas, respectively. Insulin stimulates the transport of ions, glucose and pancreatectomy, there is a profound glucagon deficiency that, in combination with insulin deficiency, can produce a metabolic crisis. It has been reported that the metabolic r t [ m t i i p i c a o r h m t c h esponse to glucagon was considerably more pronounced in otal pancreatectomy patients than in type I diabetic patients 13]. Therefore, a state of chronic glucagon deficiency may odify the effect of glucagon on the liver, presumably hrough up-regulation of glucagon receptors which results n enhanced hyperglycaemic responsiveness. Despite an ncrease in peripheral insulin receptor availability, however, ancreatogenic diabetes is also accompanied by a decrease n hepatic insulin receptor availability [14]. This paradoxial effect is probably due to a concurrent deficiency in PPs nd renders the liver resistant to the suppressant effects f insulin on hepatic glucose production. In fact, a critical ole for PP as a hormonal mediator of glucose metabolism as been suggested. This hormone is released in a biphasic anner in response to feeding and it has been shown o inhibit exocrine pancreatic secretion and gallbladder ontraction. PP receptors have also been identified on rat epatocyte plasma membranes [15]. Studies on a canine amino acids across cell membranes, has anabolic effects such as protein synthesis and lipogenesis, and has growthpromoting effects secondary to the stimulation of RNA and DNA synthesis [6]. Insulin is known to be a potent inhibitor of glucose production in the liver in humans and, under euglycaemic conditions, the intravenous infusion of insulin causes hepatic glucose production to decrease rapidly. The release of insulin into the portal vein after a glucose load causes suppression of net hepatic glucose production, stimulation of net hepatic glucose uptake and glycogen synthesis [7]. Comparing the insulin action of patients with pancreatogenic diabetes to those with type I diabetics [8], enhanced extrahepatic tissue sensitivity to physiologic hyperinsulinaemia and higher insulin binding to red blood cell receptors have been observed in patients with pancreatogenic diabetes. Insulin decay has also been

Effect of subcutaneous pancreatic tissue transplants on streptozotocin-induced diabetes in rats. II. Endocrine and metabolic functions

The present study examines the effect of subcutaneous pancreatic tissue grafts (SPTG) on endocrine and metabolic functions in streptozotocin (STZ)-induced diabetic rats using radioimmunoassay and biochemical techniques. SPTG survived even after 15 weeks of transplantation and significantly improved the weight of STZ-diabetic rats over a 15-week period. Although blood glucose-, cholesterol-, and glycosylated-haemoglobin (GHb) levels were not significantly lower in STZ-diabetic rats treated with SPTG, the values of these biochemical parameters were lower than those in untreated diabetic rats. Plasma and pancreatic immunoreactive C-peptide (IRCP) levels did not improve after SPTG (IRCP expressed as mean ± standard deviation were 0.22 ± 0.07, 0.072 ± 0.02 and 0.08 ± 0.03 pg ml−1in the plasma non-diabetic, diabetic and treated rats respectively, while IRCP levels in the pancreas of the non-diabetic, diabetic and treated rats were 433.8 ± 0.1, 22.9 ± 0.01 and 10.4 ± 0.01 pg mg tissue−1respectively). SPTG, however, improved plasma immunoreactive insulin (IRI) levels in both plasma and pancreas. IRI values in plasma were 54.7 ± 13.6, 18.0 ± 5.0 and 22.1 ± 4.3 μUI ml−1in non-diabetic, diabetic and treated rats respectively and were 277.3 ± 37.1, 14.7 ± 1.8 and 30.3 ± 15.9 μIU μg tissue−1in the pancreas of non-diabetic, diabetic and treated rats respectively. There was improvement in immunoreactive glucagon (IRG) levels after SPTG. IRG values in the plasma of non-diabetic, diabetic and treated rats were 147.0 ± 10.7, 408.0 ± 76.5 and 247.7 ± 3 pg ml−1respectively whereas, IRG measured in the pancreas was 1642.25 ± 424.23, 1899.0 ± 290.4 and 1714.1 ± 301.98 pg μg tissue−1in non-diabetic, diabetic and treated rats, respectively. The pancreas:plasma ratio of pancreatic hormones was deranged in untreated diabetes but improved after SPTG. In conclusion, SPTG significantly improved the weight gain, pancreatic insulin content, plasma IRG and pancreas: plasma ratio of IRCP, IRI and IRG. It also reduced blood glucose-, cholesterol-, and glycosylated-hemoglobin levels in STZ-diabetic rats.

Redundant parasympathetic and sympathoadrenal mediation of increased glucagon secretion during insulin-induced hypoglycemia in conscious rats

Both the parasympathetic and sympathoadrenal inputs to the pancreas can stimulate glucagon release and are activated during hypoglycemia. However, blockade of only one branch of the autonomic nervous system may not reduce hypoglycemia-induced glucagon secretion, because the unblocked neural input is sufficient to mediate the glucagon response, ie, the neural inputs are redundant. Therefore, to determine if parasympathetic and sympathoadrenal activation redundantly mediate increased glucagon secretion during hypoglycemia, insulin was administered to conscious rats pretreated with a muscarinic antagonist (methylatropine, n = 7), combined α- and β-adrenergic receptor blockade (tolazoline + propranolol, n = 5), or adrenergic blockade + methylatropine (n = 7). Insulin administration produced similar hypoglycemia in control and antagonist-treated rats (25 to 32 mg/dL). In control rats (n = 9), plasma immunoreactive glucagon (IRG) increased from a baseline level of 125 ± 11 to 1,102 ± 102 pg/mL during hypoglycemia (ΔIRG = +977 ± 98 pg/mL, P < .0005). The plasma IRG response was not significantly altered either by methylatropine (ΔIRG = +677 ± 141 pg/mL) or by adrenergic blockade (ΔIRG = +1,374 ± 314 pg/mL). However, the IRG response to hypoglycemia was reduced to 25% of the control value by the combination of adrenergic blockade + methylatropine (ΔIRG = +250 ± 83 pg/mL, P < .01 v control rats). These results suggest that the plasma glucagon response to hypoglycemia in conscious rats is predominately the result of autonomic neural activation, and is redundantly mediated by the parasympathetic and sympathoadrenal divisions of the autonomic nervous system.

Correlation between residual β-cell function and age at onset of spontaneous diabetes in Long Evans Tokushima Lean rats

We studied the natural course of disease in spontaneously diabetic rats, Long Evans Tokushima Lean (LETL) rats, to determine whether it showed similar pathogenetic heterogeneity to that of patients with insulin-dependent diabetes mellitus (IDDM) with regard to the relationships between age at onset, rapidity of disease progress, and degree of β-cell function at the time of its manifestation. Type 1 diabetes developed in 35 rats (6.3%) between 40 and 140 days of age. Eight rats that became diabetic at age 69 days or less were more severely ketotic at the time of first detection of glycosuria and showed more rapid deterioration than seven rats that became diabetic later after birth (mean plasma 3-hydroxybutyrate levels, 4,707 ± 1,215 pmol/L v 1,390 ± 859 pmol/L; mean ± SEM, P < .01). The mean plasma levels and pancreatic content of immunoreactive insulin (IRI) of the early onset rats, 47 ± 13 pmol/L and 19 ± 12 pmol/g tissue weight, were significantly lowere ( P < .01) than the corresponding values of the late-onset rats, 262 ± 52 pmol/L and 348 ± 87 pmol/g tissue weight, respectively. Both values were markedly lower than the mean values of 25 nondiabetic LETL rats, 976 ± 122 pmol/L and 3,488 ± 628 pmol/g tissue weight. Plasma immunoreactive glucagon (IRG) levels were significantly increased in the diabetic groups (early onset, 57 ± 13 pmol/L; late-onset, 51 ± 12 pmol/L; nondiabetic, 18 ± 1 pmol/L; P < .01). These changes in pancreatic hormone levels of the early onset and late-onset rats were compatible with the histological features of their pancreatic islets. The titers of plasma competitive insulin autoantibodies (CIAA) were within the normal range in all but two diabetic LETL rats. The changes in blood chemistry, pancreatic hormone content, and histology of the pancreatic islets of 13 cyclophosphamide-induced diabetic LETL rats were similar to but less marked than those of the spontaneously diabetic rats with regard to the relationship between age at onset and β-cell function at the time of manifestation of disease. These results demonstrate that LETL rats with spontaneous or cyclophosphamide-induced type 1 diabetes showed similar pathogenetic heterogeneity to that of IDDM patients with respect to the relationship between age at onset and the rapidity of progress of disease; pancreatic β cells tend to be more rapidly and severely damaged in early onset than in late-onset diabetic LETL rats.

Importance of basal glucagon in maintaining hepatic glucose production during a prolonged fast in conscious dogs.

We undertook studies in conscious dogs to assess the role of basal glucagon in stimulating glucose production after a 7-day fast. Two protocols consisting of a 40-min basal period (-40 to 0 min), and a 180-min test period (0-180 min) were used. During the test period of the first protocol (hormone replacement; n = 4), somatostatin was infused (0.8 micrograms.kg-1.min-1) along with basal intraportal replacement amounts of insulin and glucagon, whereas in the second protocol (glucagon deficiency; n = 5), somatostatin plus insulin alone were infused. Glucose production and gluconeogenesis were measured using tracer and arteriovenous difference techniques. Plasma insulin levels were similar during the test period in both protocols (6 +/- 1 microU/ml). The plasma immunoreactive glucagon level in the control protocol averaged 50 +/- 8 pg/ml, whereas in the glucagon-deficiency protocol the level fell from 50 +/- 8 to 29 +/- 8 pg/ml (P less than 0.05). The plasma glucose level and the rate of glucose production were unchanged during bihormonal replacement. During glucagon deficiency the plasma glucose level was held constant at 100 +/- 4 mg/dl by glucose infusion. Tracer-determined endogenous glucose production fell from 1.8 +/- 0.1 to 1.0 +/- 0.1 mg.kg-1.min-1 by 30 min (P less than 0.05). After 3 h of glucagon deficiency, gluconeogenic conversion of alanine to glucagon was reduced 40% and the hepatic fractional extraction of alanine was reduced by 45%. The efficiency of the gluconeogenic process within the liver was not altered by glucagon deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

All products of proglucagon are elevated in plasma from uremic patients.

We measured and characterized the proglucagon (PG) products in plasma obtained from nine uremic patients and six control subjects in the fasting state. The concentrations of PG products measured by direct RIAs were significantly higher in the uremic patients than in the normal subjects; the concentration of total glucagon immunoreactivity in plasma was 209 +/- 20 vs. 70 +/- 11 pmol/L, the glucagon-like peptide-1 immunoreactivity was 154 +/- 33 vs. 41 +/- 13 pmol/L, and the concentration of pancreatic-type glucagon immunoreactivity was 53 +/- 6 vs. 30 +/- 7 pmol/L. By chromatography, the predominating PG products in both uremic and normal plasma were shown to be glicentin [corresponding to PG-(1-69)] and the major PG fragment [presumably corresponding to PG-(72-158)]. In addition, glucagon-like peptide-1 [presumably corresponding to PG-(72-107) amide] was a major product in uremic plasma. Our results suggest that the kidneys play an important role in the removal from plasma of these products of PG.

Endocrine-Metabolic Function in Remission-Phase IDDM During Administration of Cyclosporine

We have studied the endocrine-metabolic status of patients in non-insulin-receiving (NIR) remission of insulin-dependent diabetes mellitus (IDDM) within 6-60 mo of diagnosis during administration of cyclosporine, in comparison with nondiabetic subjects. IDDM patients in NIR remission were recognized when target glycemic control (plasma glucose and mean capillary blood glucose levels less than 7.8 mM before meals) was maintained without administration of insulin for at least 2 wk. In so-called isoglycemic tests, 50 g glucose was administered orally, and the glycemic curve was simulated in a subsequent study by programmed intravenous infusion of glucose. Under these conditions, the subjects with diabetes exhibited obvious glucose intolerance: acute beta-cell responses to intravenous glucose were virtually absent but significant, although subnormal responses were present after oral glucose. The responses of plasma immunoreactive gastric inhibitory polypeptide to oral glucose were normal. After bolus intravenous injections of glucose, the patients with diabetes again exhibited glucose intolerance; acute responses of immunoreactive insulin (IRI) and C-peptide were present, although grossly obtunded. On intravenous infusion of arginine (30 g in 30 min), the patients with diabetes showed substantial but subnormal increases in plasma IRI and C-peptide. Intravenous infusion of arginine elicited increments of plasma immunoreactive glucagon (IRGI) in both groups, and this response was slightly exaggerated in the patients with diabetes. On ingestion of a standard mixed meal (Sustacal) delivering 600 cal, there was a modest but significantly greater increase in plasma glucose levels in the diabetic subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation of Glucagon Secretion by Gastric Inhibitory Polypeptide in Patients with Hepatic Cirrhosis and Hyperglucagonemia

Porcine gastric inhibitory polypeptide (GIP) was infused iv (120 micrograms in 60 min) in seven patients with biopsy-proven hepatic cirrhosis who had surgical porta-caval anastomoses and hyperglucagonemia in the postabsorptive state. The infusions resulted in elevation of blood levels of immunoreactive GIP into the upper range of those observed after ingestion of large mixed meals. This was accompanied by significant increments in immunoreactive glucagon (IRG) in the plasma. Similar infusions in two cirrhotic patients with surgical porta-caval anastomoses who had normal plasma IRG levels in the postabsorptive state had no effect on the plasma IRG level. Ingestion of triglyceride (60 g) in hyperglucagonemic cirrhotic patients with porta-caval anastomoses also resulted in elevation of plasma immunoreactive GIP, and this was again associated with significant elevation of the plasma IRG level. Chromatography studies showed that the increments in plasma IRG after the administration of GIP or triglyceride were largely accounted for by increases in pancreatic-type glucagon. There were no significant effects of administration of GIP or triglyceride on the blood levels of glucose or immunoreactive insulin. It is concluded that porcine GIP is glucagonotropic in patients with cirrhosis of the liver who show elevated levels of IRG in the plasma in the postabsorptive state. This effect is not due to diversion of portal blood to the systemic circulation and may be attributable to hypersensitivity of the alpha-cells to stimulation by GIP.

Oxytocin stimulates glucagon and insulin secretion in fetal and neonatal sheep.

In adults of several species arginine vasopressin (AVP) and oxytocin (OT) stimulate pancreatic secretion of immunoreactive plasma glucagon (IRG). In fetal sheep AVP is an important stress hormone and may be simultaneously secreted with OT; however, their effects on IRG secretion are not known. We sought to determine if AVP and/or OT affected pancreatic IRG secretion in fetal and neonatal sheep. Either AVP or OT was infused for 30 min in chronically catheterized fetal and neonatal sheep, obtaining peripheral arterial and/or portal venous blood samples before; 10, 15, and 30 min during; and 15, 30, and 60 min after infusion for measurements of blood gases, hematocrit, IRG, immunoreactive plasma insulin (IRI) and plasma glucose. AVP did not affect IRG or IRI in fetal sheep (mean +/- SE, 133 +/- 1 days gestation), but small increases occurred in portal venous blood of lambs (2-49 days old). In contrast, OT (4.6 +/- 0.3 mU/min.kg; n = 12) increased fetal plasma IRG from 72 +/- 5 to 86 +/- 6 and 97 +/- 7 pg/ml (P less than 0.001) and IRI from 16 +/- 2 to 20 +/- 3 and 20 +/- 2 microU/ml (P less than 0.02) at 15 and 30 min, respectively; 157 +/- 11 microU OT/min.kg had no effect. In lambs (2-49 days old), 3.0 mU OT/min.kg increased arterial (n = 15) IRG from 139 +/- 19 to 367 +/- 43 and 483 +/- 76 pg/ml (P less than 0.01) and portal IRG (n = 8) from 167 +/- 39 to 341 +/- 72 and 502 +/- 148 pg/ml (P less than 0.01), respectively. Arterial and portal IRI also rose (P less than 0.01) from 36 +/- 4 to 82 +/- 12 and 105 +/- 32 microU/ml and from 29 +/- 5 to 65 +/- 13 and 51 +/- 7 microU/ml, respectively. Glucose was unchanged in all experiments. In fetal and neonatal sheep, AVP has minimal effects on IRG and IRI release. In contrast, OT increases both substantially; furthermore, there is a difference in fetal and neonatal responsiveness. OT may be important in modulating glucagon and insulin secretion during and after parturition.

Effect of bonito insulin injection on plasma immunoreactive glucagon levels and carbohydrate and lipid metabolism of sea bass ( Dicentrarchus labrax)

1. 1. A single intraperitoneal injection of bonito insulin (2 IU/kg = 0.137 mg/kg) increased plasma insulin levels in sea bass throughout a period of 24 hr. 2. 2. Insulin treatment caused a pronounced hypoglycaemia at 6 and 10 hr postinjection. 3. 3. At 3 hr postinjection, plasma immunoreactive glucagon (IRG) levels in insulin-treated fish were lower than those observed in control fish. 4. 4. On the contrary, at 10 and 24 hr following injection, plasma IRG levels were significantly higher in insulin-injected fish. 5. 5. At 24 hr postinjection, insulin treatment increased muscle glycogen content whereas liver glycogen remained unaltered. 6. 6. Insulin injection decreased plasma cholesterol and free fatty acid levels, as well as increasing liver lipid content. No significant effect on lipid muscle content was observed.

Ultrastructural and functional studies of pancreatic B cells in Wistar rats treated with immunotherapeutic doses of cyclosporin

Cyclosporin (CYA) was administered to Wistar rats at immunotherapeutic doses (20 mg/kg) and the functional and morphological effects on pancreatic B cells were observed. Serum CYA levels were kept in the range that is often encountered in clinical immunotherapy in humans. The treated rats had slightly elevated plasma glucose levels; on treatment days 6 and 13, their serum immunoreactive insulin and pancreatic insulin contents were low. Plasma immunoreactive glucagon levels were slightly elevated during treatment. Glucose tolerance was impaired on day 13. These functional abnormalities disappeared 2 weeks after drug withdrawal. B cells showed ultrastructural evidence of CYA toxicity, including cytoplasmic degranulation, nuclear inclusions, and cisternal dilatation of both the rough endoplasmic reticulum and the Golgi apparatus. These changes were observed on the third day of treatment and became more pronounced on the 6th and 13th days of treatment. By the second week after drug withdrawal, most of the B cells presented a normal ultrastructure. We confirmed that a dose of CYA similar to that used in clinical immunotherapy in humans produces ultrastructural disturbances in the pancreatic B cells of Wistar rats after relatively short-term administration.

Effect of the duration of malnutrition and of nutritional rehabilitation on blood glucose homeostasis and pancreatic hormones in rats.

1. To study the efficiency of rehabilitation after different periods of protein-energy malnutrition, we used as a model preweaning malnourished rats. After weaning, male Wistar rats were fed on a protein-deficient diet (50 g casein/kg) ad lib. for the whole study (DR group) or rehabilitated with normal diet (180 g casein/kg; RR group) from weaning, week 0, or weeks 1, 3, 5, 8 and 16 thereafter. 2. Twelve animals from the DR group were killed at the beginning of each rehabilitation period. The twelve rehabilitated rats were killed after 2 weeks. Body-weight and epididymal adipose tissue weight, blood glucose, plasma immunoreactive insulin (IRI) and immunoreactive glucagon (IRG), and pancreatic contents of IRI and IRG were determined. 3. Food intake of RR rats rose significantly except during the last period where body-weight increased less than that during the previous period. Fat-pad weights increased in the same manner in DR and RR groups. 4. Blood glucose fell and plasma IRG rose significantly without any change in plasma IRI after each rehabilitation period, except during the last period where blood glucose concentrations became stable. Pancreatic IRG and IRI showed the same type of response to those of the plasma. 5. All short-term rehabilitation periods were similarly efficient at producing catch-up growth. High insulin sensitivity of target cells was responsible for good recovery except after long-term malnutrition.

Pancreatic polypeptide response to oral glucose load in patients with liver cirrhosis--interrelationship between PP and other pancreatic endocrine hormones

The purpose of the present study was to elucidate the interrelationship between pancreatic polypeptide (PP) and other pancreatic endocrine hormones. For this purpose, a radioimmunoassay (RIA) system of plasma PP was established and the changes in plasma PP, plasma immunoreactive insulin (IRI), plasma C-peptide reactivity (CPR) and plasma immunoreactive glucagon (IRG) following oral administration of glucose were examined in ten normal subjects and twenty-five patients with liver cirrhosis. Patients with liver cirrhosis were classified into a normal glucose tolerance group (NGT), an impaired glucose tolerance group (IGT), and a diabetes mellitus group (DM) on the basis of the glucose tolerance curves obtained after the oral administration of glucose. In the IGT and DM groups, fasting plasma PP levels were significantly elevated when compared with those in the control and NGT groups. Also oral administration of 75g glucose elicited an exaggerated rise in plasma PP in the IGT and DM groups when compared with the response in the control and NGT groups. On the other hand, PP response to glucose in the NGT group was similar to that in the control group. Plasma IRI increased markedly before and after oral administration of glucose in the IGT and DM groups when compared with the control groups. In these patients, plasma levels of CPR almost paralleled those of IRI. No significant difference was noted between the NGT group and the control group with regard to plasma IRI and CPR levels before and after oral glucose loading. Accordingly, insufficient insulin action was considered to exist in the IGT and DM groups. This insufficiency in insulin action was expressed in terms of the indices of increase in plasma IRI and CPR, delta IRI/delta BS and delta CPR/delta BS, which corresponded to the elevated blood glucose levels, being significantly lower in the IGT and DM groups than in the control and NGT groups 30 minutes after oral administration of glucose. No significant difference was noticeable between the NGT group and control group with regard to these indices. In the patients with liver cirrhosis, the delta PP value, obtained by subtracting the plasma PP level during fasting from the PP level 30 minutes after oral glucose loading, was inversely correlated with the values of both delta IRI/delta BS and delta CPR/delta BS.(ABSTRACT TRUNCATED AT 400 WORDS)

Correlation between minimal secretory capacity of pancreatic beta-cells and stability of diabetic control.

The significance of the minimal secretory capacity of pancreatic beta-cells for the stability of the plasma glucose level was studied in 20 patients with insulin-dependent diabetes mellitus. Changes in plasma concentrations of major counterregulatory hormones in response to hypoglycemia were also investigated in these patients to clarify their contribution to diabetic brittleness. beta-Cell function was evaluated on the basis of elevation of plasma C-peptide immunoreactivity (CPR) during the intravenous glucagon test with a highly sensitive assay for plasma CPR that could detect as little as 0.03 ng/ml. After stimulation with glucagon, a significant increase in plasma CPR was observed in 10 of the patients whose beta-cell function had been evaluated as completely depleted by a conventional assay for plasma CPR. A clear inverse correlation was found between the secretory capacity of pancreatic beta-cells measured in this way and the degree of glycemic instability (r = -.74, P less than .01). Infusion of insulin at a rate of 0.15 U.kg-1.h-1 for 60 min caused a continuous decrease in the plasma glucose level, resulting in neuroglycopenia in 7 of the 10 CPR nonresponders but only 2 of the CPR responders. During insulin-induced hypoglycemia, plasma glucagon immunoreactivity did not increase in the CPR nonresponders but increased significantly in the CPR responders. A positive correlation was found between the minimal residual beta-cell capacity and the responsiveness of alpha-cells to hypoglycemia (r = .65, P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in plasma glucagon, pancreatic polypeptide and insulin during development of alloxan diabetes mellitus in dog.

Changes in canine plasma glucose, immunoreactive glucagon (IRG), pancreatic polypeptide (PP) and insulin (IRI) were studied during the acute development of diabetes mellitus after iv alloxan injection. 100 mg or 75 mg/kg body weight of alloxan was injected iv and blood was taken successively till one or two days later. Plasma glucose showed four phases: first immediate and moderate decrease appeared 30 min after injection, second initial hyperglycemic phase, third hypoglycemic and fourth diabetic ones. Plasma IRI had already increased to 182 +/- 60 microU/ml 10 min after injection and again began to increase after about 6 h, peaking to 134 +/- 49 microU/ml at 18 h. Plasma IRG began increasing gradually soon after alloxan injection. The initial value was 196 +/- 26 pg/ml and it increased to 534 +/- 144 pg/ml at 4 h during the initial hyperglycemic phase, then reached a higher level through the hypoglycemic and diabetic phases. The change in plasma PP was similar to that in IRG. The initial value was 256 +/- 95 pg/ml at 12 h after injection, peaking to 840 +/- 100 pg/ml in the hypoglycemic phase. Similar blunted values were obtained following 75 mg/kg alloxan injection. Thus not only plasma IRI but also plasma IRG and PP varied greatly during the acute development of alloxan diabetes and some contribution of IRG to the initial hyperglycemic phase was suggested.

Effect of the enteroinsular axis on both the A- and B-cell response to arginine after oral glucose in man.

Studies were made on the effect of the enteroinsular axis on amino acid-induced insulin and glucagon secretion during hyperglycaemia in man. The responses of plasma immunoreactive insulin, C-peptide, and immunoreactive glucagon to arginine infusion were investigated in nine healthy subjects after induction of hyperglycaemia by an oral glucose load and by intravenous glucose infusion to produce similar glucose concentrations in the arterialised blood. The plasma immunoreactive insulin and C-peptide levels increased to higher levels after an oral glucose load than after an intravenous infusion of glucose. The incremental areas under the immunoreactive insulin and C-peptide curves during arginine infusion were significantly greater (p less than 0.01) after oral than after intravenous glucose administration. The plasma immunoreactive glucagon level was suppressed equally after oral and intravenous glucose loads. However, during subsequent arginine infusion, the plasma immunoreactive glucagon level rose more in the presence of hyperglycaemia induced by oral than intravenous glucose. The incremental area under the plasma immunoreactive glucagon curve during arginine infusion was 1.6-fold greater after glucose ingestion than after intravenous glucose infusion. These results suggest that the enteroinsular axis has a stimulatory effect on the responses of pancreatic A and B cells to arginine after oral glucose administration.

A large molecular form of glucagon-like peptide-1(GLP-1) immunoreactivity is co-released with glucagon from pancreas by arginine in normal subjects

Plasma immunoreactivities of glucagon-like peptide-1 (GLP-1IR) in normal subjects were measured with a specific radioimmunoassay during the arginine tolerance test. Plasma GLP-1IR after arginine infusion showed a 3-fold increase in parallel to plasma glucagon immunoreactivity and plasma glucagon-like immunoreactivity, measured with a glucagon C-terminal specific antiserum (OAL 123) and an N-terminal and/or central region specific glucagon antiserum (OAL 196), respectively. This finding suggested that the increased immunoreactivities of GLP-1 as well as that of glucagon were of pancreatic origin. Upon gel chromatography, plasma at the basal state showed three GLP-1 immunoreactive peaks, eluted in the position of void volume, synthetic GLP-1(72–108), and a smaller molecular fraction. Gel chromatography of plasma after an arginine load showed an additional peak ( M r 13000–15000) with little change in other GLP-1 immunoreactive peaks. This large molecular form of GLP-1IR was also shown to exist in the human pancreatic extract. Moreover, the free GLP-1 concentrations in plasma before and after an arginine load were shown to be about equal by reverse phase HPLC. These data suggested that in normal subjects arginine stimulation co-releases GLP-1IR, predominantly large molecular form, with glucogen from the pancreas.

Glucose Tolerance, Plasma Insulin and Immunoreactive Glucagon in Chickens Selected for High and Low Body Weight

Relationships among glucose tolerance, plasma insulin and plasma glucagon were examined in chicks developed through selection for high (HW) and low (LW) body weight at 56 d of age and F1 crosses (HL) obtained from HW males mated to LW females. At 21, 42, 63 and 84 d of age, chicks from each population were intubated with glucose (2 g/kg body wt) following a 24-h fast. Blood was collected at 20-min intervals up to 100 min postadministration. At all ages, the LW chicks were better able to clear glucose from their blood than were their HW counterparts, and the HL chicks exhibited intermediate responses. Impaired glucose tolerance in the HWs and HLs was not associated with insulin insufficiency; the HWs and HLs, in comparison to the LWs, exhibited higher plasma concentrations of insulin at 42 and 63 d of age and plasma insulin levels did not differ significantly among populations at 21 or 84 d of age. Plasma immunoreactive glucagon responses to glucose intubation were inconsistent at the different ages; however, concentrations were consistently higher in the HWs and HLs than in the LWs. It was concluded that excessive fat deposition in chickens selected for rapid growth is associated with increased concentrations of insulin and glucagon in plasma and perhaps insulin resistance.

Plasma Immunoreactive Somatostatin Response to Arginine After Glycemic Control With Continuous Subcutaneous Insulin Infusion in Type I Diabetics

The effects of 3 wk of near normoglycemia by continuous subcutaneous insulin infusion (CSII) on plasma immunoreactive somatostatin (IRS) responses to arginine (0.5 g X kg-1 X 30 min-1) in seven patients with insulin-dependent diabetes mellitus (IDDM) were compared with the same patients in poor glycemic control during conventional insulin therapy (CIT) and with seven normal controls. After 3 wk of CSII treatment, mean daily blood glucose and HbA1 decreased to mean (+/- SE) values of 129 +/- 6 mg/dl and 8.0 +/- 0.1%, respectively. Plasma free-insulin levels in IDDM patients 30 min before a meal during CSII were significantly higher than those during CIT or in normal controls. Fasting mean plasma IRS levels of the IDDM patients during CSII (7.3 +/- 1.4 pg/ml) were not different from those during CIT (8.4 +/- 1.3 pg/ml) and in normal controls (5.9 +/- 0.8 pg/ml). Arginine elicited a rise in plasma IRS during CIT in all seven IDDM patients during CIT and in the normal controls, with peak values of 18.2 +/- 4.1 and 12.5 +/- 1.8 pg/ml, respectively. However, no significant increase in plasma IRS was observed in all seven IDDM patients during CSII. The integrated values of plasma IRS during the arginine-infusion study of the IDDM patients treated with CIT were significantly higher than those of the normal controls. The increased integrated values of plasma immunoreactive glucagon response to arginine observed during CIT became normalized after CSII. These results suggest that glycemic control with CSII in IDDM patients suppresses the increased plasma IRS response to arginine that occurs during CIT.(ABSTRACT TRUNCATED AT 250 WORDS)

Response of plasma glicentin to intraduodenal administration of glucose in piglets

Controversial results concerning the secretion of glicentin prompted us to investigate the response of circulating glicentin to intraduodenal administration of glucose in piglets. A 20% solution of glucose (2 g/kg) was administered into the duodenum of six piglets in a fully conscious state. As blood glucose rose, plasma insulin increased to a peak of 21 +/- 4 microU/ml. Plasma glucagon, determined by C-terminal-specific antiserum, was 70 +/- 30 pg/ml at fasting and slightly increased after the glucose load. Plasma immunoreactive glucagon measured by cross-reacting glucagon antiserum increased from the baseline of 1563 +/- 260 to a peak of 4738 +/- 415 pg/ml at 120 min. Plasma glicentin determined by antiserum R 64 was 463 +/- 81 pmol/l at baseline and reached a peak level of 1081 +/- 174 pmol/l at 90 min. The percent changes of plasma glucagon from the fasting level measured by cross-reacting antiserum and glicentin were 296 and 233%, respectively. There was a significant correlation between plasma glucagon measured by cross-reacting antiserum and glicentin (r = 0.817, P less than 0.001). Chromatography of plasma obtained during glucose load revealed the heterogeneity of glicentin. It can be concluded from the present study that glicentin is clearly secreted in response to intraluminal administration of glucose.