Immunoreactive Glucagon Levels Research Articles

Classic Article: Commentary on “Metabolic Studies in Total Parenteral Nutrition with Lipid in Man. Comparison with Glucose

A study was undertaken of patients on a regimen of total parenteral nutrition comparing the nitrogen balance, energy substrates, blood amino acids, immunoreactive insulin, and immunoreactive glucagon levels during the sequential infusion of nonprotein calories as either glucose alone (glucose system) or 83% as Intralipid (Pharmacia Fine Chemicals, Montreal, Canada) and 17% glucose (lipid system). These nonprotein calories were administered with a constant background of amino acids (1 g/kg per day), vitamins, and minerals. Each system was infused for a week at a time and the order of infusion randomized. In some patients whole blood arteriovenous (A‐V) levels of amino acids were measured across forearm muscle. During the glucose system there was a significantly higher level of pyruvate, lactate, alanine, and immunoreactive insulin, consistent with glucose being the principal source of energy. In contrast, during the lipid system there was a rise in free fatty acids and ketone bodies with a fall in insulin, suggesting that lipid was now the principal source of energy. Despite these two very diverse metabolic situations the nitrogen balance with both systems was positive to a comparable degree after the establishment of equilibrium. Correspondingly, A‐V differences of whole blood amino acid nitrogen showed uptake by muscle to an equivalent degree with both systems. Clinical studies indicated that the lipid system as defined herein could be infused by peripheral vein for up to 43 days with resultant weight gain, elevation of serum proteins, and healing of fistulae. Our studies suggest that for both metabolic and clinical reasons exogenously infused lipid is a suitable source of nonprotein calories. (J Clin Invest 57:125–136, 1976)

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.

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.

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.

Changes in Plasma Glucose, Insulin, Glucagon, Catecholamine, and Glycogen Contents in Tissues during Development of Alloxan Diabetes Mellitus in Rats

Alloxan monohydrate (ALX) was given to rats (20 mg/100 g body weight) and plasma glucose (PG), immunoreactive insulin (IRI), immunoreactive glucagon (IRG), and catecholamine (CA) as well as the glycogen (G) content in the liver, muscle, and kidneys were measured. Although whether hypoglycemia was present immediately after injection was not clear, the PG level increased, with a modest peak after 2 h. The PG levels in rats receiving food 6 h after ALX injection increased substantially after 1 h and continued to increase after 24 h. Although the IRI level increased slightly 10 min after the injection, low amounts were present for up to 24 h due to continued fasting. There was a rise in the IRG level at 10 min after injection, and then it decreased again slowly to a low level during fasting. No change was observed in the CA level. Hepatic G further decreased at 30 min after ALX injection and started to increase from 2 h to a peak level after 18 h. Almost no changes were noted in muscle tissues. The G content in the renal cortex remained almost unchanged, although it tended to decrease slightly after 8 h. When rats were fed 6 h after ALX injection, the IRI level rose slightly. Hepatic G at 6 h after feeding was nearly equal to that during feeding itself, but it then decreased rapidly. Muscular G became equal to that during feeding. Renal G showed a clear tendency to increase 6 h after feeding and became about four times that during periods when rats were fed ad lib. In conclusion, not only PG, IRI, and IRG, but also tissue G levels were shown to change markedly in the early stage of ALX induced diabetes.

Changes in immunoreactive insulin, C-peptide immunoreactivity, and immunoreactive glucagon in acute viral hepatitis

Insulin and glucagon are thought to play important roles as hepatotrophic factors in acute viral hepatitis (AVH); however, few reports have investigated the responses and relationships of each of these hormones to liver damage in detail. We studied insulin and glucagon responses during the acute and recovery phases of AVH. We performed a glucose tolerance test (GTT) and an insulin sensitivity test (IST) in each phase in 11 patients with AVH. In 8 additional patients in the acute phase (total n = 19), were compared immunoreactive insulin (IRI) and C-peptide immunoreactivity (CPR) levels with transaminase levels. In the acute phase, IRI concentrations were normal from fasting to 60 min, despite an increased CPR level. In the recovery phase, IRI and CPR levels increased significantly. Immunoreactive glucagon levels in both phases did not differ significantly from those in controls. During the IST, the insulin sensitivity index in both phases was significantly lower than that in the controls. Fasting IRI and sigma IRI showed significant negative correlations with transaminase levels. We found enhanced insulin secretion and a decrease in plasma insulin in the acute phase of AVH. The discrepancy between IRI and CPR responses in the acute phase suggests an increase in the degradation or consumption of insulin in the liver.

Relationship between arterial and portal vein immunoreactive glucagon during exercise.

The importance of changes in glucagon in the regulation of hepatic glucose production (Ra) during exercise has been questioned, as an increase in arterial immunoreactive glucagon (IRG) is not always detectable. However, IRG in the portal vein (PV) and not in the artery is most relevant, as flow through PV is approximately 80% of liver blood flow. To assess the extent that arterial IRG reflects the levels the liver is exposed to in PV, dogs (n = 5) were implanted with catheters in a carotid artery, hepatic vein (HV), and PV. Dogs were studied > or = 16 days later during rest and 150 min of moderate treadmill exercise, with indocyanine green and [3-3H]glucose infused to assess hepatic plasma flow (HPF) and hepatic Ra. IRG was 66 +/- 7, 73 +/- 8, and 81 +/- 7 pg/ml in the artery, HV, and PV at rest; it rose at 10 and 150 min of exercise to 89 +/- 9 and 127 +/- 13 pg/ml in the artery, 106 +/- 17 and 186 +/- 21 pg/ml in HV, and, by considerably more, to 153 +/- 20 and 261 +/- 25 pg/ml in PV. HPF fell by approximately 30% with exercise. The fall in HPF accounted for < 11% of the increased arterial-to-PV IRG gradient during exercise, with increased splanchnic IRG release comprising the remainder. Ra was linearly related to IRG levels in the three vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of pancreatic glucagon gene expression in mice bearing a subcutaneous glucagon-producing GLUTag transplantable tumor.

Transgenic mice that express a glucagon gene-simian virus-40 large T-antigen (GLUTag) fusion gene develop neuroendocrine carcinoma of the large bowel. This glucagon-producing tumor was implanted sc and reproducibly formed tumors in nude mice. The transplanted GLUTag tumor expressed large amounts of proglucagon mRNA transcripts, and the levels of proglucagon mRNA transcripts remained constant during 2-8 weeks of tumor growth. The posttranslational processing of proglucagon in the transplantable tumor resembled that detected in the original transgenic tumor, with the liberation of glicentin, oxyntomodulin, glucagon, glucagon-like peptide (1-37) [GLP-1-(1-37)] and GLP-1-(7-37). Tumor-bearing mice demonstrated progressive elevations in the plasma levels of proglucagon-derived peptides. Elevated plasma levels of glucagon-like immunoreactive peptides and immunoreactive glucagon were associated with a marked reduction in the levels of pancreatic glucagon mRNA transcripts by 4 weeks, and after 8 weeks of tumor growth, the levels of glucagon mRNA transcripts in the pancreas were not detectable by Northern blot analysis. Synthesis of the proglucagon-derived peptides was also significantly suppressed at 4-8 weeks in the pancreas of tumor-bearing animals. Histological examination of the endocrine pancreas in mice carrying the GLUTag tumor for 6-8 weeks demonstrated a marked reduction in the number and size of the islets of Langerhans and a disproportionately greater decrease in the number of cells exhibiting glucagon immunoreactivity. By electron microscopy, the residual A-cells were small, compressed at the periphery of the islets, and had poorly developed cytoplasmic organelles. In contrast, no changes in mouse glucagon gene expression or islet morphology were detected in control animals without tumors or mice carrying a sc v-jun-induced fibrosarcoma. The suppression of pancreatic A-cell function and islet size in mice with elevated plasma levels of the proglucagon-derived peptides raises the possibility that a proglucagon-derived peptide may participate in a negative feedback loop, inhibiting expression of the glucagon gene in the A-cells of the endocrine pancreas.

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)

Dynamic and Static Phases of Severe Dietary Obesity in Sheep: Food Intakes, Endocrinology and Carcass and Organ Chemical Composition

The chronology of changes in body weights, food intakes and plasma concentrations of selected metabolic hormones and metabolites were determined in sheep during the induction (dynamic) and static phases of diet-induced obesity. Lean adult Dorset ewes weighing 47 kg were fed a pelleted hay-grain diet at maintenance (lean; n = 7) or were fed the same diet ad libitum to a maximum intake of 3 kg·sheep-1·d-1 (obese; n = 8) for 78 wk. Body weight of obese sheep doubled (97 vs. 47 kg) by wk 42 of ad libitum intake. Average daily intakes of dry matter (12.8 g/kg) and digestible energy (165 kJ/kg) were comparable in maintenance-fed lean sheep and ad libitum-fed obese sheep consuming maintenance after wk 50, which began the static phase of obesity. Fasting plasma concentrations of insulin in the obese sheep increased steadily from 50 ± 6 pmol/L at wk 0 to a sustained plateau of 249 ± 21 pmol/L after wk 30. Plasma levels of glucose, immunoreactive glucagon and thyroid hormones were consistently greater (P < 0.05) in obese sheep than in lean sheep after wk 2, 3 and 25, respectively, of the experiment. Concentration of lipid (49 vs. 25%) in the carcass stripped of internal fat was greater (P < 0.01) in obese sheep than in lean sheep, but concentration of protein (10.4 vs. 15.3%) was less in the heavier carcass (58 vs. 24 kg) of the obese sheep. We conclude that hyperinsulinemia and abnormal fuel metabolism are early events during dynamic obesity and these defects persist throughout the static phase of obesity. Maintenance energy requirements relative to unit body weight (W1.0) seem similar in lean and dietary obese sheep.

Glucagon administration to the rat via eye drops.

Systemic absorption of glucagon from eye drops containing an emulsant caused an elevation in blood D-glucose concentrations in anesthetized rats. Glucagon (0.03 mg) delivered to the eye in buffered saline had no significant hyperglycemic action. However, delivery of glucagon in eye drops containing 0.25% saponin caused a rapid, dose-dependent increase in blood D-glucose values. Maximal absorption was observed 20 minutes after eye drop administration and values returned to baseline after 60 minutes. Immunoreactive glucagon levels measured 20 minutes after administration of eye drops containing saponin plus glucagon were increased by 2.4-fold compared to basal values. Glucagon administration via eye drops was ineffective when 0.5% Brij78 or BL-9 was substituted for saponin. These results demonstrate that in the rat, systemic absorption of glucagon delivered in eye drops is possible, but the choice of an emulsant may be critical.

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.

Developmental and Tissue-Specific Regulation of Proglucagon Gene Expression*

The pattern of glucagon gene expression and the posttranslational processing of proglucagon was studied in the fetal and neonatal rat. Pancreatic immunoreactive glucagon (IRG) and glucagon-like immunoreactivity (GLI) were low in both fetal pancreas and intestine, respectively. Immediately after birth, pancreatic IRG rose markedly and reached a peak concentration at postnatal day 7, followed by a gradual return to its adult level. Intestinal GLI was low until postnatal day 7 and rose steadily thereafter to adult levels. The levels of GLI in the hypothalamus were much lower than in intestine, yet the developmental accumulation of hypothalamic GLI resembled the pattern observed in intestine. In contrast, the levels of GLI and IRG in the brain stem were higher in the fetus and neonate, and decreased to adult levels. Proglucagon mRNA transcripts, uniform in size, were detected in RNA isolated from fetal or adult brainstem, pancreas, and intestine. However, fetal proglucagon mRNA transcripts were larger than adult proglucagon mRNA transcripts in pancreas and intestine, but not brainstem. The results of RNAse mapping studies, including analysis of both the 5'- and 3'-ends of the mRNA transcripts, demonstrated that the larger fetal mRNA transcripts could be accounted for by an increase in the length of the polyadenylate tail in the fetal tissues. These observations demonstrate that the developing rat exhibits tissue-specific differences in both proglucagon gene expression and the pattern of posttranslational processing of the prohormone.

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.

Glucagon Degrading Activity

To evaluate the effect of glucagon degrading activity (GDA) on radioimmunoassay (RIA) of glucagon, I measured GDAs in plasma, serum, lysed red blood cells (RBC), and suspension of mononuclear cells and granulocytes. Serum levels of GDA in patients with various diseases were also examined. 1. Serum GDA values in normal subjects (control) measured by TCA precipitation method were 4.6 +/- 2.2% (mean +/- S.D.). GDA values in plasma treated with citrate and those in serum treated with aprotinin were not different from those in nontreated serum. GDAs in plasma treated either with EDTA and aprotinin or with EDTA alone were significantly lower than those in control serum, but the values in plasma treated with heparin were markedly higher than those in control serum. 2. GDAs in RBC lysate and suspension of mononuclear cells and granulocytes remained low up to the concentration of 23 X 10(4) RBC/microliters and 5000 mononuclear cells or granulocytes/microliters, respectively. GDAs in RBC lysate and mononuclear cells were markedly suppressed by the treatment with EDTA, whereas GDAs in granulocytes were inhibited by the treatment with aprotinin. 3. Markedly high values of GDA were obtained in serum of patients with pancreas diseases, liver diseases, renal diseases and hyperthyroidism. However, in four patients these elevated levels were restored to normal value after recovery from these disorders. The elevated GDA values in serum were suppressed to normal value by the addition of EDTA and aprotinin. 4. On Bio-Gel P-6 column chromatography, 125I-glucagon incubated with patient serum containing high GDA values revealed several peaks eluted after 125I-glucagon. 5. In healthy subjects, immunoreactive glucagon (IRG) levels in nontreated serum were not different from those in plasma treated either with EDTA and aprotinin or with heparin. 6. In patients showing high serum GDA levels, serum GDA levels were not significantly related to IRG levels in plasma treated with EDTA and aprotinin. These results indicate that a series of treatment of blood samples before assay: addition of EDTA and aprotinin to the blood samples, immediate separation of plasma from blood cells, and storage at 4 degrees C is recommended to avoid breakdown of glucagon by GDAs.

Effects of portacaval shunt, transposition, and dimethylnitrosamine-induced chronic liver injury on pancreatic hormones and amino acids in dog

The effect of portacaval shunt on amino acid metabolism and pancreatic hormone secretion remains a subject of controversy. This might be due to the fact that shunt has two consequences; it shunts portal blood into the systemic circulation, and it causes hepatic parenchyma dysfunction by decreasing total hepatic blood flow. In order to see which one of these two is the more important factor, we created a model of portacaval transposition in dogs (PCT) causing portal systemic shunting without impairing hepatic blood flow and compared it with a model of hepatic dysfunction in dogs created by administering dimethylnitrosamine (DMNA). The dynamics of amino acid levels and pancreatic hormone secretion in the portal blood were investigated. DMNA dogs and dogs with a standard end-to-side portacaval shunt (Eck) showed elevated immunoreactive glucagon (IRG) levels and low immunoreactive insulin (IRI) levels in the portal blood as well as an amino acid imbalance, while values in PCT dogs were similar to those of controls. These data suggested that high IRG and low IRI in the portal blood and amino acid disturbances in the dogs with Eck shunts were due to hepatic parenchyma dysfunction, rather than to portal-systemic shunting.

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.

Biochemical changes in rhesus monkey during the first days after streptozotocin administration are indicative of selective β cell destruction

Hormonal and glycemic changes in 22 rhesus monkeys were characterized during the first days after treatment with streptozotocin (STZ) (45 to 55 mg/kg, administered intravenously [IV]. Almost half ( 10 22 ) of the monkeys developed insulin-dependent diabetes mellitus (STZ-IDDM) within five days following injection. Four of the remaining monkeys did not become insulin dependent for at least 6 months after STZ treatment, during which time they were considered non-insulin-dependent, and eight monkeys never required exogenous insulin. In the STZ-IDDM group, plasma immunoreactive c-peptide (IRC-P) levels fell by three hours after STZ from a mean ± SEM of 252 ± 82 to 101 ± 45 pg/mL, as glucose and immunoreactive glucagon (IRG) levels increased from 65 ± 3 and 120 ± 37, respectively, to 336 ± 43 mg/dL and 234 ± 52 pg/mL, respectively. Between six and 30 hours after treatment, IRC-P increased to a peak of 1,561 ± 360 pg/mL before falling permanently to <60 pg/mL by 66 hours. During this period, glucose and IRG responded in a reciprocal fashion by falling and then increasing to levels above 300 mg/dL and 300 pl/mL, respectively, by 66 hours. In the non-insulin-dependent diabetes mellitus (STZ-NIDDM) group, no clear reciprocal relationship between IRC-P and glucose and IRG was obtained. In nine additional monkeys subjected to total pancreatectomy (Px), IRC-P and IRG levels fell immediately and permanently by >90% and 75%, respectively. Levels of immunoreactive somatostatin increased steadily over the initial 96 hours following STZ, but did so in both STZ-IDDM and Px monkey groups. Plasma lipid hydroperoxide levels measured in two monkeys that developed STZ-IDDM were unchanged during the first 96 hours after STZ administration. In conclusion, the glycemic and hormonal pattern observed with STZ-IDDM rhesus monkeys during the first days following treatment is indicative of selective pancreatic β-cell destruction resulting from a direct action of STZ.

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.