Showing papers on "Insulin published in 1974"

Insulin-Dependent Regulation of Insulin Receptor Concentrations: A Direct Demonstration in Cell Culture

Abstract: Chronic (5-16 hr) exposure of cultured human lymphocytes to 10-8 M insulin at 37° in vitro produced a decrease in insulin receptor concentrations unaccounted for by simple occupancy of sites; acute exposure (0-2 hr) was without effect. These results reproduced observations in vivo where chronic hyperinsulinemia (e.g., 10-8 M insulin in the circulation of obese insulinresistant hyperglycemic mice) is associated with a substantial reduction in the concentration of insulin receptors per cell, while acute hyperinsulinemia in vivo has no effect on receptor concentration. These data suggest a reciprocal relationship between insulin in the extracellular fluid and the concentration of insulin receptors per cell, which is mediated at the target cell itself by intracellular insulin-sensitive regulatory processes and directly affects target-cell sensitivity to hormone.

Catecholamines: mediator of the hypermetabolic response to thermal injury.

Abstract: Hypermetabolism characterizes the metabolic response to thermal injury and the extent of energy production is positively related to the rate of urinary catecholamine excretion. Alpha and beta adrenergic blockade decreased metabolism from 69.6 +/- 5.3 Kcal/m(2)/hr to 57.4 +/- 5.2 (p < 0.01), and infusion of 6 microgm epinephrine/minute in normal man significantly increased metabolic rate. Twenty noninfected burned adults with a mean burn size of 45% total body surface (range 7-84%) and four normal controls were studied in an environmental chamber at two or more temperatures between 19 and 33 C with vapor pressure constant at 11.88 mm Hg. All burn patients were hypermetabolic at all temperatures studied and their core and mean skin temperatures were significantly elevated above control values. Between 25 and 33 C ambient, metabolism was unchanged in controls and burns of less than 40% total body surface (48.9 +/- 4.6 Kcal/m(2)/hr vs. 48.9 +/- 4.5), but metabolic rate decreased in larger burns in the warmer environment (72.0 +/- 1.9 vs. 65.8 +/- 1.7, p < 0.001). At 21 C, metabolism and catecholamines increased, except in four nonsurvivors who became hypothermic with decreased catechol elaboration. Metabolic rate in ten patients with bacteremia was below predicted levels while catecholamines were markedly elevated suggesting interference with tissue uptake of the neurohormonal transmitters. Feeding burn patients or administering glucose and insulin improved nitrogen retention and altered substrate flow but did not significantly reduce urinary catecholamines or metabolic rate. Burned patients are internally warm, not externally cold, and catecholamines appear to mediate their increased heat production. Hypermetabolism may be modified by ambient temperature, infection, and pharmacologic means. Alterations in hypothalamic function due to injury, resulting in increased catecholamine elaboration, would explain the metabolic response to thermal injury.

Somatostatin: Hypothalamic Inhibitor of the Endocrine Pancreas

Abstract: Somatostatin, a hypothalamic peptide that inhibits the secretion of pituitary growth hormone, inhibits basal insulin secretion in fasted cats and rats. In fasted baboons both basal and arginine-stimulated secretion of insulin and glucagon are inhibited. Somatostatin appears to act directly on the endocrine pancreas. The action is dose-related, rapid in onset, and readily reversed.

Effects of Weight Reduction on Obesity STUDIES OF LIPID AND CARBOHYDRATE METABOLISM IN NORMAL AND HYPERLIPOPROTEINEMIC SUBJECTS

Abstract: Considerable controversy exists over the purported role of obesity in causing hyperglycemia, hyperlipemia, hyperinsulinemia, and insulin resistance; and the potential beneficial effects of weight reduction remain incompletely defined. Hypertriglyceridemia is one of the metabolic abnormalities proposed to accompany obesity, and in order to help explain the mechanisms leading to this abnormality we have proposed the following sequential hypothesis: insulin resistance --> hyperinsulinemia --> accelerated hepatic triglyceride(TG) production --> elevated plasma TG concentrations. To test this hypothesis and to gain insight into both the possible role of obesity in causing the above metabolic abnormalities and the potential benefit of weight reduction we studied the effects of weight loss on various aspects of carbohydrate and lipid metabolism in a group of 36 normal and hyperlipoproteinemic subjects. Only weak to absent correlations (r = 0.03 - 0.46) were noted between obesity and the metabolic variables measured. This points out that in our study group obesity cannot be the sole, or even the major, cause of these abnormalities in the first place. Further, we have observed marked decreases after weight reduction in fasting plasma TG (mean value: pre-weight reduction, 319 mg/100 ml; post-weight reduction, 180 mg/100 ml) and cholesterol (mean values: pre-weight reduction, 282 mg/100 ml; post-weight reduction, 223 mg/100 ml) levels, with a direct relationship between the magnitude of the fall in plasma lipid values and the height of the initial plasma TG level. We have also noted significant decreases after weight reduction in the insulin and glucose responses during the oral glucose tolerance test (37% decrease and 12% decrease, respectively). Insulin and glucose responses to liquid food before and after weight reduction were also measured and the overall post-weight reduction decrease in insulin response was 48% while the glucose response was relatively unchanged. In a subgroup of patients we studied both the degree of cellular insulin resistance and the rate of hepatic very low density (VLDL) TG production before and after weight reduction. These subjects demonstrated significant decreases after weight reduction in both degree of insulin resistance (33% decrease) and VLDL-TG production rates (40% decrease). Thus, weight reduction has lowered each of the antecedent variables (insulin resistance, hyperinsulinemia, and VLDL-TG production) that according to the above hypothesis lead to hypertriglyceridemia, and we believe the overall scheme is greatly strengthened. Furthermore, the consistent decreases in plasma TG and cholesterol levels seen in all subjects lead us to conclude that weight reduction is an important therapeutic modality for patients with endogenous hypertriglyceridemia.

A Model of the Kinetics of Insulin in Man

Abstract: The design of the present study of the kinetics of insulin in man combines experimental features which obviate two of the major problems in previous insulin studies. (a) The use of radioiodinated insulin as a tracer has been shown to be inappropriate since its metabolism differs markedly from that of the native hormone. Therefore porcine insulin was administered by procedures which raised insulin levels in arterial plasma into the upper physiologic range. Hypoglycemia was prevented by adjusting the rate of an intravenous infusion of glucose in order to control the blood glucose concentration (the glucose-clamp technique). (b) Estimation of a single biological half-time of insulin after pulse injection of the hormone has been shown to be inappropriate since plasma insulin disappearance curves are multiexponential. Therefore the SAAM 25 computer program was used in order to define the parameters of a three compartment insulin model. The combined insulin mass of the three compartments (expressed as plasma equivalent volume) is equal to inulin space (15.7% body wt). Compartment 1 is apparently the plasma space (4.5%). The other two compartments are extra-vascular; compartment 2 is small (1.7%) and equilibrates rapidly with plasma, and compartment 3 is large (9.5%) and equilibrates slowly with plasma. The SAAM 25 program can simulate the buildup and decay of insulin in compartments 2 and 3 which cannot be assayed directly. Insulin in compartment 3 was found to correlate remarkably with the time-course of the servo-controlled glucose infusion. Under conditions of a steady-state arterial glucose level, glucose infusion is a measure of glucose utilization. We conclude that compartment 3 insulin (rather than plasma insulin) is a more direct determinant of glucose utilization. We suggest that the combined use of glucose-clamp and kinetic-modeling techniques should aid in the delineation of pathophysiologic states affecting glucose and insulin metabolism.

An Artificial Endocrine Pancreas

Abstract: In order to regulate the blood sugar in the intact depancreatized dog as precisely as that accomplished by its normal pancreas, specific equipment has been devised to deliver insulin or glucose continuously and establish normoglycemia both in the fasting and glucose-loaded states. A minicomputer was programmed to respond to the constantly monitored whole blood glucose by injecting appropriate insulin or glucose intravenously to maintain or restore the normal blood sugar. Standardized glucose challenges consisting of uniform infusions of 10 mg. glucose per kg. min. for sixty minutes were applied to assess the performance of the artificial pancreas. Direct control which relates insulin dosage to the level of the circulating blood sugar results in a response to the challenge resembling mild maturity-onset diabetes both in the abnormally high blood sugar response to glucose loading and in the large amount of insulin required to effect a return to normoglycemia. In contrast, control based on projected (predicted) values of blood sugar not only prevents the abnormal rise but consumes in some cases only 10 per cent of the insulin used for the same glucose load. The performance of the system parallels that of the normal pancreas and lends support to the hypothesis that biphasic insulin responses to glucose challenges are essential for the economy of insulin and the precision of regulation seen in healthy subjects.

Plasma Norepinephrine and Epinephrine in Untreated Diabetics, During Fasting and After Insulin Administration

Abstract: Employing a precise and sensitive double-isotope derivative technic, plasma norepinephrine and epinephrine were measured in twenty-three normal subjects and fourteen diabetics during various metabolic conditions. Patients with poorly controlled diabetes showed a rise in norepinephrine, which correlated with the degree of metabolic derangement, during resting conditions. High epinephrine values were seen only in patients with moderate to severe ketoacidosis. During exercise, diabetic patients with ketosis demonstrated large increments in plasma catecholamines as compared to normals. During insulin treatment, when good control had been achieved, plasma catecholaniine levels were similar to those in normal subjects. During prolonged fasting, plasma norepinephrine rose from 0.18 to 0.40 ng. per milliliter in four normal nonobese subjects. No change was observed in plasma epinephrine. During insulin hypoglycemia, high plasma epinephrine levels were seen only in subjects in whom the blood glucose concentration declined to values below 20 mg. per 100 ml. Plasma norepinephrine rose as blood glucose concentrations decreased even in diabetics in whom values had not reached hypoglycemic levels. No correlation was observed between plasma epinephrine and increase in pulse rate during hypoglycemia.

Characterization of the Insulin and Somatomedin-C Receptors in Human Placental Cell Membranes

Abstract: Human placentas have been used to further investigate the binding of insulin and somatomedin to cell membrane receptors. Conditions for optimal binding of 125I-insulin were defined for both participate membrane preparations and membranes solubilized in Triton X-100. Human placental membranes are a rich source of high affinity insulin receptors. As in previous studies with rat liver and fat cell preparations, only somatomedin and proinsulin were effective competitors for binding to the insulin receptor. These findings were used to define the optimal conditions for a competitive binding assay for insulin and insulin-like peptides. This assay had threshold sensitivities of 10 μU/ml for insulin and less than 0.1 U/ml for somatomedin. Incubation at 4 C for 15–18 hr essentially eliminated proteolytic degradation of the labeled hormone and led to strikingly better binding than was observed at higher temperatures. A highly purified preparation of somatomedin-C labeled with radioactive iodine was found to...

Clinical Control of Diabetes by the Artificial Pancreas

Abstract: An artificial pancreas capable of maintaining blood sugar homeostasis within the physiological range is described in this paper. The blood sugar is continuously monitored and then interpreted by a minicomputer which in turn controls and implements the delivery of insulin (or glucose). The entire system is automatic and by giving insulin according to a projected blood sugar level the pattern of insulin administration is similar to the biphasic response of the normal pancreas. Five parameters for control can be selected and altered at will so that any level of normoglycemia can be maintained. Hypoglycemia is not encountered, and none of the patients experienced any side effects during or after the trials. The clinical trials involved a two-day study. On the first day the blood sugar profiles were monitored throughout the day. The patients were given their usual doses of subcutaneous insulin and ate measured meals and snacks. On the second day, they received no subcutaneous insulin; insulin was administered intravenously in accordance with the moment-to-moment requirements of the patients who were given meals the same as those of the previous day. Graphs plotted on a common time scale compare the blood sugar patterns on the two successive days and show the significant improvement in blood sugar homeostasis achieved by this artificial pancreas.

Membrane potential of beta-cells in pancreatic islets.

Abstract: Intracellular microelectrode techniques have been used to investigate the membrane potential and electrical activity of β-cells of Langerhans islets of mice. In Krebs-Henseleit solution containing substimulatory glucose concentrations, i.e. concentrations which do not produce an insulin release, β-cells showed no electrical activity. In this concentration range an increase of glucose concentration depolarized the membrane without inducing spike activity. The β-cells became electrically active in glucose concentrations known to produce insulin secretion. The type of electrical activity depended on glucose concentration. Between 5.5 and 16.6 mM glucose it generally occured in bursts. Each was initiated by a depolarization of about 10 mV to a plateau level from which irregular spikes with frequencies up to 12/sec arose. The burst ended with a repolarization phase to the original potential level. With increasing glucose concentration the duration of the bursts increased and the intervals between the bursts shortened. Above 16.6 mM glucose the burst activity usually changed into continuous activity. If the relative duration of burst activity is plotted against glucose concentration there is a sigmoid relationship similar to that known to exist between insulin release and glucose concentration. TTX had no effect on burst activity. Removal of [Ca]o inhibited burst activity. Occasionally at zero [Ca]o action potential-like spikes were observed. Re-introduction of [Ca]o initially increased the frequency of these action potential-like spikes and then led to the usual glucose induced burst activity. The significance of the results is discussed in relation to the mechanism of insulin release.

Diabetogenic effect of streptozotocin in the rat during the perinatal period.

Abstract: The diabetogenic effect of streptozotocin was investigated in the rat during the fetal and neonatal life. Streptozotocin was directly injected in the vitellin vein of the fetus or in the saphenous vein of the neonate. In the 21.5 day old fetus, diabetogenic activity was demonstrated with a single dose of 100 μg/gm. administered the day before, and this was indicated by a fall in the pancreatic insulin content to 20 per cent and a lowering of the plasma insulin to 60 per cent of the controls. A single dose (100 μg/gm.) of streptozotocin administered on the day of birth produced an overt diabetes in the neonate: the maximal fall in the pancreatic insulin content (7 per cent of the controls) was observed four days after the streptozotocin injection, during the highest blood glucose level (300 per cent of the controls). A significant increase in the pancreatic glucagon content was observed twenty-four hours after the maximal insulin depletion. Liver glycogen content was occasionally decreased. More severe diabetes was obtained by two streptozotocin injections (50μg/gm.), with lowest pancreatic and highest blood glucose levels at 1 per cent and 60 per cent, respectively. A clearcut drop of the plasma insulin/glucose ratio was observed in the drug-treated animals. Three weeks after injection(s), basal blood glucose and plasma insulin levels were normal, although impairment of insulin secretion still appeared after glucose load and insulin pancreatic content was still slightly lower. A rapid and spontaneous, if not quite complete recovery, is a characteristic pattern of the streptozotocin diabetes in the neonate as compared to that in the adult.

Characterization of the Effects of Arginine and Glucose on Glucagon and Insulin Release from the Perfused Rat Pancreas

Abstract: To characterize the mechanisms by which arginine and glucose affect pancreatic alpha and beta cell function, the effects of these agents over their full dose response, both alone and in various combinations, were studied using the perfused rat pancreas. Arginine (0-38 mM), in the absence of glucose, stimulated biphasic glucagon (IRG) secretion (Km approximately 3-4 mM) at concentrations less than 1 mM and caused nonphasic insulin (IRI) release (Km approximately 12-13 mM) but only at concentrations greater than 6 mM. Glucose (0-27.5 mM) alone stimulated biphasic IRI release (Km approximately 9-10 mM) at concentrations in excess of 5.5 mM and caused nonphasic inhibition of IRG secretion (Kt approximately 5-6 mM) at concentrations as low as 4.1 mM. These results demonstrate fundamental differences in pancreatic alpha and beta cell secretory patterns in response to glucose and arginine and suggest that glucagon secretion is more sensitive to the effect of both glucose and arginine. Various concentrations of arginine in the presence of 5.5 mM glucose stimulated biphasic IRG and IRI release: IRG responses were diminished and IRI responses were enhanced compared with those seen with arginine in the absence of glucose. Glucose (0-27.5 mM) in the presence of 3.2 or 19.2 mM arginine caused similar inhibition of IRG secretion (Km approximately 5-6 mM) and stimulation of IRI release (Km approximately 9-10 mM) as that seen with glucose alone, although greater IRG and IRI release occurred. This augmentation of IRI secretion was greater than that expected from mere additive effects of glucose and arginine. Classical Lineweaver-Burk analysis of these results indicates that glucose is a non-competitive inhibitor arginine-stimulated glucagon secretion and suggests that glucose and arginine affect pancreatic alpha and beta cell function via different mechanisms. In addition, comparison of simultaneous insulin and glucagon secretion patterns under various conditions suggests that endogenous insulin per se has little or no direct effect on IRG secretion and that endogenous glucagon does not appreciably affect pancreatic beta cell function.

Studies of insulin, growth hormone and prolactin binding: ontogenesis, effects of sex and pregnancy.

Abstract: The ontogenesis of specific binding of 125I-labeled insulin, hGH and oPRL was measured in tissues from rat, rabbit and guinea pig. Binding of 125I-oPRL and 125I-hGH was very low in liver membranes from fetal and immature rats. A 9- fold (oPRL) and 3.5-fold (hGH) increase in binding occurred between 20 and 40 days of age with a greater increase in binding in mid and late pregnancy. Binding to male liver membranes was significantly lower at all stages of development. There were no significant changes in the binding of 125I-hGH from fetal through 30 day rabbit liver membranes. Between 30 and 60 days of age, a 6-fold increase in binding occurred, with a further increase in binding during pregnancy. A similar overall pattern was observed with I25I-bGH. The increase in specific binding of 125I-oPRL was more gradual and occurred earlier than for 125I-GH. In the guinea pig, three patterns of 125I-insulin binding with respect to development were observed. Fetal placenta and kidney showed marked increase in specifi...

Effects of somatostatin on plasma glucose and glucagon levels in human diabetes mellitus. Pathophysiologic and therapeutic implications.

Abstract: To evaluate the role of pancreatic alpha-cell dysfunction in human diabetes mellitus, somatostatin, an inhibitor of glucagon secretion, was infused (1 mg over two hours) in 10 insulin-dependent diabetic subjects. Fasting plasma glucagon fell from 150 ± 15 (mean ± S.E.M.) to 77 ± 10 pg per milliliter (p<0.001), and plasma glucose from 260 ± 20 to 191 ± 21 mg per 100 ml (p<0.001). Similar responses occurred in a hypophysectomized diabetic patient, indicating that these effects of somatostatin were independent of suppression of growth hormone secretion. Somatostatin (4 mg subcutaneously) was active transiently. In additional studies, somatostatin infusion combined with insulin completely abolished post-meal hyperglycemia in four diabetic patients and was more effective than insulin alone. These results indicate that excessive glucagon secretion accounts for about 25 per cent of the fasting plasmaglucose levels in such patients. Furthermore, somatostatin may be a useful adjunct to insulin in treating...

Treatment of Diabetic Coma with Continuous Low-dose Infusion of Insulin

Abstract: Thirty-eight patients in diabetic coma from four different centres were treated with a continuous low-dose intravenous infusion of insulin at an average dose of 7·2 IU/hr. All patients recovered rapidly except for one profoundly shocked patient who died. The mean fall in plasma glucose was 58% four hours after the start of insulin. Blood ketone bodies and plasma free fatty acids showed a similar response. There was no significant difference in plasma glucose response according to severity of acidosis or previous treatment with insulin. Hypokalaemia was uncommon. In the treatment of diabetic coma this technique has proved simple, safe, and effective.

Evidence for the Involvement of Sulfhydryl Oxidation in the Regulation of Fat Cell Hexose Transport by Insulin

Abstract: Previous studies have shown that the oxidants Cu++, H2O2, and diamide mimic the stimulatory effect of insulin on 3-O-methylglucose transport in isolated fat cells. The present experiments were designed to determine whether sulfhydryl oxidation plays a key role in the activation of the glucose transport system. It was found that reductants such as dithiothreitol inhibited 3-O-methylglucose transport rates and that this effect was reversible when cells were washed free of reducing agent. Treatment of cells with 1 mM N-ethylmalcimide for 5 min completely blocked the actions of insulin and oxidants on hexose transport without affecting control transport system activity. Under these conditions, binding of 125I-labeled insulin to fat cell surface receptors was inhibited by only about 50%. Addition of insulin or oxidants to fat cells for 10 min before addition of N-ethylmaleimide completely prevented the inhibitory effect of N-ethylmaleimide on the activated transport system. This protective effect on transport rates appears to reside at a site that is altered by insulin subsequent to hormone-receptor interaction, since prior treatment of fat cells with insulin did not prevent the partial inhibitory effect of N-ethylmaleimide on insulin receptors. Furthermore, treatment of cells with N-ethylmaleimide after incubation with insulin prevented the elevated transport rates from returning to control levels when either the cells were washed free of hormone or insulin binding to its receptors was disrupted by trypsin digestion. However, transport rates in these cells treated with N-ethylmaleimide remained sensitive to cytochalasin B, phlorizin, and reductants. These data suggest that a component of the glucose transport system in isolated fat cells must be maintained in its disulfide state for expression of transport activity. Further, the results are consistent with the concept that the binding of insulin to cell surface receptors triggers sulfhydryl oxidation in this component, which prevents its reaction with N-ethylmaleimide.

Splanchnic glucose and amino acid metabolism in obesity.

Abstract: Arterial concentrations and splanchnic exchange of glucose, lactate, pyruvate, glycerol, free fatty acids, and individual acidic and neutral amino acids were determined in obese and nonobese control subjects in the basal state and during a 45 min infusion of glucose. Glucose was administered to the controls at a rate (2 mg/kg/min; 144 +/- 4 mg/min) known to inhibit splanchnic glucose output without influencing peripheral glucose utilization. The obese subjects received glucose at two dose levels (75 and 150 mg/min) which simulated either the rise in insulin or the inhibition in splanchnic glucose production observed in the controls. In the basal state splanchnic glucose production did not differ significantly between obese and control subjects. However splanchnic uptake of lactate, glycerol, alanine, free fatty acids, and oxygen was 50-160% greater in obese subjects. Splanchnic uptake of glucose precursors could account for 33% of hepatic glucose output in the obese group as compared to 19% in controls. The increase in alanine and lactate uptake was due in part, to a 50% increase in splanchnic fractional extraction. Administration of glucose to the control subjects 144 +/- 4 mg/min) resulted in a 50-60% increment in arterial insulin and a 75% reduction in splanchnic glucose output. In the obese group, infusion of glucose at a rate of 75 mg/min resulted in an equivalent rise in arterial insulin, but was accompanied by a less than 40% inhibition in splanchnic glucose output. Glucose infusion at a rate of 150 mg/min in the obese resulted in a 75% reduction in splanchnic glucose output which was equivalent to that observed in controls, but was accompanied by a significantly greater rise (100-200%) in arterial insulin. It is concluded that in obesity (a) despite basal hyperinsulinemia, splanchnic uptake of glucose precursors is increased, the relative contribution to total glucose release attributable to gluconeogenesis being 70% higher than in controls; (b) infusion of glucose at rates causing equivalent increases in arterial insulin induces a smaller inhibition in splanchnic glucose output than in controls; (c) infusion of glucose at rates causing comparable inhibition in splanchnic glucose output is accompanied by a disproportionately greater increase in endogenous insulin than in controls. These data are compatible with hepatic resistance to insulin in obesity.

Effect of somatostatin in patients with acromegaly: suppression of growth hormone, prolactin, insulin and glucose levels.

Abstract: In five patients with acromegaly, the chronic hypersecretion of growth hormone was effectively inhibited by the administration of synthetic somatostatin (intravenous bolus of 250 μg followed by a constant infusion, 500 μg per 45 minutes). The rate of growth hormone decline during the infusion was rapid, with a mean half-time of 24 minutes. After the infusion, a return of secretion to previously elevated levels was observed. These data suggest that the inhibitory action of somatostatin on growth hormone secretion is nearly complete and that the biologic action of somatostatin is brief. In addition, somatostatin induced a concomitant fall in circulating levels of insulin, glucose and prolactin and an increase in fatty free acids. No effect on levels of thyrotropin, follicle-stimulating hormone or luteinizing hormone was observed. (N Engl J Med 290:935–938, 1974)

Increased "glucagon immunoreactivity" in plasma of totally depancreatized dogs.

Abstract: Elevated plasma glucagon immunoreactivity (IRG) observed in overt diabetes and during prolonged fasting is assumed to be the result of increased secretion of pancreatic glucagon. In seven healthy mongrel dogs diabetes was induced by total pancreateetomy During the first two weeks following surgery, porcine NPH (6 to 12 U, once daily) and Regular insulin (6 to 12 U twice daily) were administered. Thereafter, insulin treatment was discontinued and the dogs were fasted for periods up to seven days. Plasma IRG was measured using antiglucagon serum G9-I which is 95 per cent specific for pancreatic glucagon. Fifteen hours after the last insulin injection an intraportal infusion of Regular insulin was given in amounts sufficient to achieve normoglycemia: mean IRG (pg./ml.) was 118 ± 34, a value similar to that observed in the fasting intact animals (134 ± 33). After insulin withdrawal, as fasting continued, plasma IRG increased progressively in all dogs. On Days 5 and 6-7, after insulin withdrawal, when peripheral plasma insulin was undetectable and marked hyperglycemia, hyperlipacidemia and ketonuria prevailed, mean IRG was 624 ± 136 and 986 ±184, respectively. The highest level of IRG observed was 1450 in one dog on Day 7. These results are confirmed by using three other antiglucagon sera considered to be specific for pancreatic glucagon. We conclude that: 1) Progressively increasing amounts of material crossreacting with “specific” antiglucagon sera appear in plasma of totally depancreatized dogs fasting for up to seven days. 2) This event appears to be the consequence of metabolic derangements induced by insulin lack. 3) Hyperglucagonemia can result onoly from a defect of the pancreatic α cell, but can also be the consequence of excessive production of IRG from a nonpancreatic source. It could be that glucagon deficiency cannot be easily demmonstrated, because the release of nonpancreatic IRG can compensate for lack of pancreatic glucagon.