IRI) And Glucagon Research Articles

Suppressive effect of long term sulfonylurea treatment on A, B, and D cells of normal rat pancreas.

The effect of chronic administration of tolbutamide (150 mg/kg X day, orally, over 60 days) and glibenclamide (1 mg/kg X day, orally, over 60 days) on pancreatic A, B, and D cell function was investigated in male nondiabetic rats. In a first set of experiments pancreatic hormonal response to metabolic stimuli was evaluated during glucose (11.1 mM) or arginine (10 and 20 mM) infusion in the isolated perfused rat pancreas. The basal levels of insulin (IRI) and glucagon (IRG) were similar in control and in sulfonylurea-treated rats. Tolbutamide treatment markedly depressed the IRI response to glucose (P less than 0.005) or arginine (P less than 0.0005) infusion and the IRG response to arginine (P less than 0.01). After glibenclamide treatment, IRI decreased significantly (P less than 0.0005 and P less than 0.005, respectively) only in response to arginine infusion. This effect was still evident 10 days after the end of treatment. Furthermore, long term glibenclamide administration suppressed somatostatin (SRIF) response to glucose (P less than 0.0005) or arginine (P less than 0.0005). In a different group of rats treated with glibenclamide (1 mg/kg X day, orally, over 60 days) IRI, IRG, and SRIF plasma concentration and blood glucose levels were examined at the end of treatment. The results did not differ significantly from those of a control group. In the same animals, pancreatic IRI, IRG, and SRIF content, measured on acid-ethanol extracts, was reduced (P less than 0.1 vs. controls). These data clearly indicate that long term treatment with sulfonylurea drugs has a suppressive effect on pancreatic endocrine function in rats. The concomitant involvement of A, B, and D cell suggests that this effect is not specific.

Glucagon release after stimulation of the lateral hypothalamic area in rats: predominant beta-adrenergic transmission and involvement of endorphin pathways.

Catheterization of the portal vein and stereotaxic implantation of electrodes in the lateral hypothalamic area (LHA) were performed in normal rats after thiopental anesthesia. Immunoreactive glucagon (IRG) and insulin (IRI), glucose, catecholamines, and beta-endorphin were monitored in portal and peripheral plasma, before and during electrical stimulation of the LHA. The influences on glucose and hormone concentrations of propranolol, phentolamine, atropine, and naloxone infusions were also investigated in similar rats. A basal portoperipheral concentration gradient was found for IRG, IRI, and catecholamines, but not for beta-endorphin. The LHA stimulation induced a significant rise in portal catecholamine, IRG, and glucose concentrations; IRI remained unchanged; the portoperipheral catecholamine gradient was augmented. These alterations were not observed after bilateral splanchnicectomy. Propranolol infusion abolished the LHA-dependent IRG and glucose rises. Naloxone reduced the IRG rise significantly. Phentolamine and atropine did not modify the LHA-induced reactions. These results suggest that the glucagon release which follows LHA electrical stimulation depends mainly on beta-adrenergic transmission by the splanchnic nerves. Opioid peptide receptors may modulate this effect.

Study of A- and B-cell function in beta-thalassemia major.

Hepatic and pancreatic damage owing to iron overload is often present in patients with beta-thalassemia major. In order to investigate B-cell function and hepatic insulin clearance in these patients, under a high transfusion program and regular chelation therapy, we studied the glucose (BG), insulin (IRI) and C-peptide (CPR) response and the CPR/IRI ratio after OGTT in 27 patients with Cooley's anemia and in 10 sex- age- and weight-matched healthy subjects; we also studied BG and IRI levels after IVGTT in 9 beta-thalassemic patients and in 9 control subjects. Furthermore, BG, CPR, IRI and glucagon (IRG) response to arginine infusion were evaluated in 5 thalassemic patients with normal OGTT and in 5 age-, sex- and weight-matched normal children, in order to assess pancreatic A-cell function, too. OGTT and IVGTT were normal in the patients with beta-thalassemia major. Plasma IRI level 30 min after an oral glucose load and the insulinogenic index for cumulative intervals were significantly lower in thalassemics after OGTT, whereas the insulin response and insulinogenic index were normal following i.v. glucose. No significant difference was observed for the CPR/IRI ratio during OGTT between thalassemics and normal subjects. Finally, BG, CPR, IRI and IRG levels were similar in the thalassemic patients and in healthy children both fasting and following arginine infusion. Our data suggest that patients with beta-thalassemia major, under a high transfusion program and regular chelation therapy, may have normal glucose tolerance and normal hepatic insulin clearance in spite of iron overload in pancreas and liver. Insulin response to oral glucose was lower than the one to IVGTT, probably because of diminished secretion of the gastrointestinal hormones which stimulate insulin release.

STUDIES ON THE APPLICATION OF 75 g ORAL GLUCOSE TOLERANCE TEST IN VARIOUS LIVER DISEASES

Seventy five g oral glucose tolerance test (OGTT) has been recently proposed. Little is known, however, on the results by the new test in various liver diseases.Studies were conducted with 59 patients with liver diseases : 11 acute viral hepatitis (AVH), 5 chronic inactive hepatitis (CIH), 14 chronic active hepatitis (CAH), 13 liver cirrhosis (LC), 10 fatty liver (FL) and 6 hepatic fibrosis (HF). Eighteen healthy volunteers served as control. Blood samples were taken at 0, 30, 60, 90, 120 and 180 min after oral loading of 75 g glucose, and stored frozen until radioimmunoassay for immunoreactive insulin (IRI) and glucagon (IRG). Blood sugar levels were determined by glucose oxidase method.The results obtained herein were as follows : (1) None of the patients studied showed fasting blood sugar level more than 140 mg / dl. In contrast, 29 % of CAH, 23 % of LC and 17 % of HF had blood sugar level more than 200 mg / dl at 120 min, indicating the diabetic type (A committee report on the diagnosis of diabetes mellitus, Japan, 1982).(2) Exaggerated IRI responses to glucose stimulation were observed in most of the patients with liver diseases, particularly in LC and CAH.(3) A significant elevation in the basal IRG level was observed in LC. Circulating IRG levels tended to be suppressed by glucose.(4) The mean values of insulinogenic index (Δ IRI / Δ BS, 30 min) appeared to be higher in liver diseases than in diabetes mellitus, as described previously (AVH 2.26, CIH 0.64, CAH 0.81, LC 1.15, FL 1.32, HF 0.65).From these observations, it is concluded that approximately 20 % of CAH, LC and HF belongs to the diabetic type, according to 75 g OGTT. The degree of glucose intolerance in patients with liver diseases is relatively mild. However, we should emphasize that serum IRI response to glucose may be useful in the differential diagnosis between glucose intolerance in liver diseases and diabetes mellitus.

Glucose intolerance following cis-platinum treatment in rats

cis-Dichlorodiammineplatinum ( cis-Pt) is a heavy metal complex used in cancer chemotherapy. Since this drug has been shown to induce hyperglycemia in rats, these studies were initiated to elucidate the effects of cis-Pt on carbohydrate tolerance and insulin and glucagon secretion. Two days following i.v. cis-Pt (2.5 or 7.5 mg/kg, 5 ml/kg) or vehicle administration to male F-344 rats, plasma glucose, immunoreactive insulin (IRI) and glucagon (IRG) concentrations were determined in the basal state and serially following a glucose load (2 g/kg, i.p.). Since cis-Pt induces a dose-related anorexia, a pair-fed control group was also studied. Admnistration of 7.5 mg/kg cis-Pt was associated with plasma glucose concentrations 2.5–5 time greater than ad-libitum and pair-fed controls at every time point during the 2-h glucose tolerance test. Although basal plasma IRI concentrations of the 7.5-mg/kg group were comparable to ad-libitum fed controls, they were significantly greater than those of pair-fed partners. Furthermore, ther appropriate IRI response to a glucose stimulus observed in both controls and the 2.5-mg/kg group was absent in the 7.5-mg/kg group. Basal plasma IRG concentrations of the 7.5-mg/kg group were approximately 3–4 times greater than ad-libitum and pair-fed controls and were not suppressed following a glucose load. These results suggest that cis-Pt induces marked glucose intolerance in association with an impaired IRI response and abnormal glucagon response to a glucose stimulus.

Adrenergic modulation of glucagon and insulin secretion in obese and lean humans.

The adrenergic modulation of immunoreactive insulin (IRI) and glucagon (IRG) secretion was studied in 5 massively obese subjects hospitalized ion a metabolic ward. Epinephrine was infused alone or in combination with propranolol, a beta adrenergic blocking drug, or with phentolamine, an alpha adrenergic blocking drug. Epinephrine infusion produced a significant (p less than .02) rise in IRG levels which was blocked by addition of either phentolamine or propranolol. Pure alpha adrenergic stimulation with propranolol-epinephrine infusion inhibited IRG secretion (p less than .02). IRI levels decreased with propranolol-epinephrine infusion (p less than .02), increased with phentolamine-epinephrine infusion, and were not affected by infusion of epinephrine alone. Glucose concentrations rose with all 3 infusions but were less with phentolamine-epinephrine. A control group of 4 lean outpatients on a ad lib diet demonstrated a similar pattern but the changes of IRG secretion were smaller than in the obese subjects and were not statistically significant. We conclude that in obese humans IRI secretion is increased by beta adrenergic stimulation, is decreased by alpha adrenergic stimulation, and is unaffected by combined alpha and beta adrenergic stimulation. In contrast, IRG secretion is stimulated by combined alpha and beta adrenergic stimulation, is inhibited by pure alpha adrenergic stimulation, and is unaffected by pure beta adrenergic stimulation.

Effect of Islet-Activating Protein (IAP), Purified from the Culture Medium of Bordetella pertussis, on the Secretion of Immunoreactive Insulin and Glucagon in Normal, Alloxan-Treated, and Depancreatized Dogs

Islet-activating protein (IAP) is a new active substance purified from the culture medium of Bordetella pertussis. This active protein possesses a molecular weight of 77,000 and an isoelectric point of pH 7.8. The nature of IAP action is characterized by the enhancement of insulin secretory response to glucose and other stimuli. In this experiment, the effect of IAP on the secretion of immunoreactive insulin (IRI) and glucagon (IRG) was investigated in conscious normal, alloxan-treated, and depancreatized dogs. On the 8th day after IAP injection, in normal and alloxan-treated dogs during the infusion of arginine or glucose, the plasma glucose level was lower and the IRI level was significantly higher compared with the saline controls. The IRG level showed no significant difference between IAP and saline control groups of normal dogs, but in alloxan-treated dogs the IRG level was significantly lower when compared with the saline control. This effect of IAP disappeared on the 30th day after injection in normal and alloxan-treated dogs. However, in depancreatized dogs, there was no effect on plasma glucose and gastrointestinal IRG levels. Anti-IAP antibody was not detected by PHA before or after IAP injection in any dogs, although a marked increase of heart rate was observed. These findings suggest that (1) IAP had an insulinotropic effect in dogs, (2) insulin deficiency induced by alloxan was partially overcome by IAP, (3) the effect of IAP on glucagon secretion might be secondarily related to the enhancement of insulin secretion, although a direct glucagon-lowering effect in alloxan-treated dogs could not be excluded, (4) a single administration of IAP did not produce anti-IAP antibody, and (5) an increase of heart rate was observed after IAP injection.

246 A STUDY 0F THE STRUCTURAL AND BIOCHEMICAL DEVELOPMENT OF HUMAN FETAL ISLETS OF LANGERHANS

Variably-sized, histologically intact islets were isolated from 14 human fetal pancreases (12.0-19.5 wks. gestation) and grouped according to gestation age, region of the pancreas (splenic and duodenal) and diameter sizes. The mean number of cells/islet, based on DNA/islet was ∼30,000 (>300μm diameter), ∼11,000 (200-300μm), ∼3,500 (100-200μm) and ∼2,000 (<100μm). In both duodenal and splenic islets and all sizes the mean concentration of insulin (IRI) and glucagon (IRG) and somatostatin (IRS), expressed as pg or pg equivalents of insulin, glucagon and somatostatin per islet simultaneously increased significantly in three distinct step-wise developmental tiers: (1) 12.0-14.5 wks, (2) 15.0-18.5 wks, (3) 19.0-19.5 wks. In contrast, pancreatic poly-peptide (IRPP) concentration did not. At all fetal ages and islet sizes, content of IRI, IRG and IRS was significantly greater than IRPP in splenic islets while IRPP was greater in duodenal islets. Mean hormone ratios at all ages and sizes indicate IRI content is significantly greater than IRG and IRPP but not IRS. In summary, a precise pattern of multiphasic hormone development of IRI, IRG and IRS as well as the relative importance of IRS-containing D cells has been uncovered in human endocrine pancreas during fetal ages 12.0-19.5 wks.

The effect of COOH-terminal peptides of cholecystokinin on the exocrine and endocrine pancreas in the rat (author's transl)

Recently, the predominant molecular forms of cholecystokinin (CCK) in extracts of tissues from the central nervous system and small intestines of adult man and hog have been demonstrated to correspond to the COOH-terminal octa- and tetra-peptide of CCK. CCK is one of the established gastro-intestinal hormones capable of stimulating pancreatic exocrine secretion. In addition, pure natural porcine CCK, synthetic COOH-terminal octa-peptide of CCK and synthetic caerulein which contains a COOH-terminal penta-peptide identical to CCK have been shown to stimulate insulin and glucagon secretion in vivo and in vitro. Thus, it seems reasonable to expect some effect of these COOH-terminal fragments of CCK on pancreatic exocrine and endocrine secretion. The present study was, therefore, undertaken to compare the various COOH-terminal fragments of CCK with those effects on pancreatic exocrine and endocrine secretion in the rat.Pancreases from male Wistar rats, fed ad libitum, were isolated according to the technique of Kanno. Perfusate consisted of a Krebs Ringer bicarbonate buffer containing 4.6% Dextran T-70 and 0.25% bovine serum albumin. The effects of various COOH-terminal peptides of CCK (synthetized by Prof. Noboru Yanaihara, Shizuoka) at the doses ranging from 10-11 to 10-8M were studied in the presence of 50mg/dl or 150mg/dl glucose. Insulin (IRI) and glucagon (IRG) levels in the portal effluent were determined by radioimmunoassay using polyethyleneglycol and charcoaled dextran with antiserum 30K, respectively. Amylase activities in the pancreatic juice were assayed by a chromogenic method with blue-dyed starch polymer.In the presence of 50mg/dl glucose, IRI and IRG responses to the COOH-terminal octa-peptide of CCK (CCK-8) occurred at high doses, more than 10-9M. On the other hand, IRI and IRG releasing doses of CCK-8 resulted in lower rates of release of fluid and amylase when compared with those stimulated by the maximally effective doses of CCK-8.In the presence of 150mg/dl glucose, CCK-8 at a submaximally effective dose of 10-10M for the exocrine pancreas potentiated the IRI response to glucose stimulation. These results were completely consistent with our previous findings obtained with natural porcine CCK and caerulein. The COOH-terminal deca-peptide (CCK-10) and tetradeca-peptide (CCK-14) at a dose of 10-10M also potentiated the effluent IRI response to glucose stimulation. However, the IRI responses to CCK-8 and CCK-14 were biphasic, but the IRI response to CCK-10 was monophasic and transient. Moreover, the maximal IRI response just after the perfusion of these peptides was greater in CCK-8 than in CCK-10 or CCK-14. On the other hand, the effluent IRI responses to the COOH-terminal tetra-peptide of CCK (CCK-4) or deamidated CCK-8 (CCK-8-OH) at a dose of 10-10M was not significantly increased as compared to that obtained with glucose stimulation alone. In addition, the combined perfusion with 10-10M CCK-8 and 10-8M CCK-8-OH resulted in a lower IRI response than that obtained with the perfusion of CCK-8.From these observations, it may be concluded that CCK-8 at a submaximally effective dose for the exocrine pancreas has a glucose-dependent insulinotropic action and that the amino acids from the position 5 to 8 of the COOH-terminus and the NH2 -residue of the COOH-terminal phenylalanine are important for the insulinotropic action of CCK.

Glucagon (IRG) and insulin (IRI) response to arginine (ARG) in the rat pancreas in vitro: effect of histamine (HA) and serotonin (5HT).

Glucagon (IRG) and insulin (IRI) response to arginine (ARG) in the rat pancreas in vitro: effect of histamine (HA) and serotonin (5HT).

Physiologic effects of epinephrine on glucose turnover and plasma free fatty acid concentrations mediated independently of glucagon.

SUMMARY It has been suggested that the effects of epinephrine on glucose production by the liver may be mediated through glucagon. To investigate this possibility, epinephrine (EPI) (0.2 or 0.1 μg/kg-min) was infused in 12 conscious normal dogs with or without somatostatin (ST) (0.05 μg/kg-min), a known inhibitor of glucagon and insulin release. EPI (0.2 μg/kg-min) induced a sustained hyperglycemia. This resulted from both an increase in glucose production, which rose initially to 45% above basal and then plateaued at suprabasal levels, and a small but noticeable reduction (18%) in the metabolic clearance rate of glucose. Plasma levels of both immunoreactive glucagon (IRG) and insulin (IRI) also increased transiently. ST plus EPI resulted in a more severe hyperglycemia, which was due to an exaggerated initial peak of glucose production. This response occurred despite a clear suppression (71%) of IRG below basal. ST blunted the initial EPI-induced IRI peak, but IRI never fell below basal with the combined infusion of EPI and ST. The blunting of this initial insulin peak may have affected the hyperglycemie response to EPI. The lower dose of EPI (0.1 μg/kg-min) had a similar but less definite effect on glucose regulation and caused both insulin and glucagon levels to rise. However, at the lower EPI dose, ST had no appreciable effect on insulin release (as judged by peripheral IRI levels), although IRG was again greatly suppressed. Neither the EPI-induced hyperglycemia nor the rapid rise in glucose production was affected by ST, suggesting that the EPI-induced hyperglycemia is not mediated through glucagon release. It also appears that elevated EPI levels can compensate for the role of basal glucagon in regulation of basal glucose production in the postabsorptive state. EPI induced a transient 120% rise in free fatty acid (FFA) levels. The rise in FFA was more marked and more sustained when ST was given together with EPI irrespective of whether the initial EPI-induced insulin peak was blunted or remained unaltered, thus indicating a possible effect of ST on EPI-induced lipoly-sis. The same low dose of ST (0.5 μg/kg-min) infused without EPI greatly suppressed both IRG and IRI below basal (60%). Thus (1) EPI infusion induced sustained hyperglycemia, resulting from a transient increase in glucose production and an inhibition of metabolic clearance of glucose; both IRG and IRI were also transiently increased. (2) The effect of EPI on glucose production was independent of glucagon, but it was possibly enhanced by suppression of the initial insulin peak. (3) A low dose of ST, which, by itself, suppressed basal IRI and IRG release, was able to override the effect of EPI on IRG but not on IRI release. Thus, the effect of a selective glucagon suppression could be studied. (4) EPI increased plasma FFA only transiently. (5) ST may directly or indirectly increase the lipolytic effect of EPI.

Role of the autonomic nervous system in the mediation of LHA electrical stimulation-induced effects on insulinemia and glycemia

The short-term effects of bilateral electrical stimulation of the lateral component of the lateral hypothalamic/medial forebrain bundle area (LHA) on peripheral plasma levels of glucose (G), immunoreactive insulin (IRI) and glucagon (IRG) were measured in food-deprived, anesthetized rats in the presence of continous low i.v. glucose infusion. In normal rats LHA stimulation induced a rapid but moderate rise in IRI in the presence of a simultaneous rapid rise in G. At the end of the 5 min stimulation period the glucose-induced IRI response was clearly attenuated. In rats receiving a continous phentolamine (i.v.) infusion, the rapid IRI response was much larger in spite of only marginal rises of G. These findings suggest that electrical LHA stimulation activates two opposing mechanisms on IRI secretion, an excitatory component which is masked in the normal animal by a sympathetic α-adrenergic inhibitory component. In an attempt to define the mediating pathway of this LHA stimulation-induced IRI excitatory component, both the parasympathetic and sympathetic divisions of the autonomic nervous system were pharmacologically and surgically manipulated, all in the presence of phentolamine infusion. Neither bilateral subdiaphragmatic vagotomy, atropine, propranolol infusion, nor spinal cord transection at T1 were able to block the IRI response. These findings are consistent with a humoral mediation of this IRI stimulatory response and support the existence of a lateral hypothalamic or hypophyseal factor which is released by LHA stimulation. The implications and physiological role of the LHA in the neural control of insulin secretion and ingestive behavior are discussed.

Pancreatic glucagon response to glucose in hyperlipoproteinaemia with and without abnormalities in carbohydrate metabolism.

Abstract. The pancreatic glucagon (IRG) and insulin (IRI) secretion patterns were studied in 19 normal weight healthy male subjects without a family history of diabetes, and in 24 male patients with endogenous hyperlipoproteinaemia, by means of a 2 h-glucose infusion (12 mg/kg/min) primed by an initial injection of 0.33 g/kg. The hyperlipoproteinaemic group consisted of 8 non-obese subjects with normal carbohydrate tolerance (group A), 8 non-obese (group B) and 8 obese (group C) subjects with maturity onset type diabetes mellitus controlled diet alone. Group B was characterized by a lack of IRI-response to glucose whereas a hyperinsulinaemia was found both in group A and C. The fasting IRG levels increased from controls (29.7 ± 2.3 pmol/1) to group A (36.7 ± 6.5 pmol/l; n.s.), group B 47.3 ± 8.8 pmol/l; P &lt; 0.05) and group C (57.7 ± 8.2 pmol/l; P &lt; 0.01). In group A the IRG concentration pattern was comparable with that of the controls. On the contrary, in groups B and C the IRG levels remained significantly higher inspite of the excessive hyperglycaemia achieved by the glucose infusion, suggesting a reduced suppressibility of the alpha cell function to glucose. In addition, the latter groups were characterized by a lack of an IRG rebound after termination of the glucose infusion. No correlation was found between hyperglycaemia and the degree of IRG rebound in all groups so far studied. A diminished molar IRI-IRG-ratio was found in group B whereas an increase ratio was recorded in groups A and C during glucose infusion. There were no correlation between IRG secretion and relative body weight, carbohydrate tolerance or IRI-response to glucose. Our findings suggest a normal alpha cell response to glucose in hyperlipoproteinaemia without obesity and carbohydrate intolerance. The abnormal alpha cell function in non-obese and obese hyperlipoproteinaemics with maturity onset type diabetes mellitus is a feature characteristic of diabetes than of hyperlipoproteinaemia.

The effect of caerulein or cholecystokinin on pancreatic endocrine and exocrine secretion in the isolated perfused rat pancreas (author's transl)

Since Meade et al. reported the insulinotropic effects of the extracts of intestinal mucosa, many investigators have shown that cholecystokinin (CCK) is one of the gastrointestinal hormones stimulating insulin secretion. Contrary to these observations, Rabinovitch et al. observed no effect of pure preparations of CCK on insulin secretion and also pointed out that only crude preparations of CCK had a stimulating action on the β cell of the pancreatic islet. Recently, the insulinotropic effect previously attributed to CCK has been suggested to be due to contaminating gastric inhibitory polypeptide (GIP) present in crude preparations of CCK, not to CCK itself. Moreover, GIP has been demonstrated to potentiate the glucose-stimulated insulin release and had been found to be released by the intraduodenal administration of glucose and protein. More recently, synthetic octapeptide of CCK and synthetic caerulein, of which C-terminal pentapeptide was identical to that of CCK, have also been shown to stimulate insulin and glucagon secretion. However, it was difficult to discuss whether the insulinotropic action of these peptides administered exogenously was physiological or not because the plasma levels of CCK to which effects of exogenous CCK should be compared are unknown. The present study was, therefore, undertaken to make clear whether physiological concentrations of highly purified natural porcine CCK or synthetic caerulein have an insulinotropic effect in the isolated perfused rat pancreas. Since the well-known physiological action of CCK is its activity to increase secretion of amylase by the pancreas, insulinotropic effects of these peptides were investigated by paying attention to pancreatic exocrine secretion.Wistar strain male rats weighing 250-300g were used in all experiments. The pancreases were isolated according to the technique of Kanno and perfused with a Krebs Ringer bicarbonate buffer containing 4.6% Dextran T-70 and 0.25% bovine serum albumin. The effects of caerulein of the doses ranging from 0.01 to 100 ng/ml and CCK from 0.1 to 250 mU/ml were studied in the presence of 50,100,150 and 200 mg/dl glucose in the perfusion medium. Insulin (IRI) and glucagon (IRG) levels in the portal effluent were determined by radioimmunoassay using polyethylene glycol and charcoaled dextran with antiserum 30 K, respectively. Amylase activity in the pancreatic juice was assayed by a chromogenic method with blue-dyed starch polymer.In the presence of 50 mg/dl glucose, IRI and IRG releases were stimulated only with high doses of CCK or caerulein, i.e., more than 50mU/ml or 1 ng/ml. Moreover, the IRI and IRG responses to any doses were over in 5 min despite the prolonged infusion of the peptides. On the other hand, IRI and IRG releasing doses of CCK or caerulein resulted in lower rates of release of fluid and amylase when compared with those stimulated by the maximally effective dose of CCK or caerulein.The possibility that IRI stimulation by pure natural porcine CCK might depend, at least in part, on the contaminating GIP can be excluded under this experimental system where a glucose concentration of 50 mg/dl was used, because an infusion of GIP at a concentration of 5 ng/ml known to be effective at 100 mg/dl glucose, has been revealed to be ineffective at 80 mg/di glucose. Moreover, the concentration of GIP may be less than the threshold dose to stimulate IRI release at 50 mg/di glucose, even if highly purified preparations of CCK from G.I.H. Laboratory may have contained 10% (actually 1 to 2%) by weight of GIP. The concentration of GIP in the 50 mU/ml CCK could be calculated as 1.43 ng/ml (CCK; 3500 Units = 1 mg). Similarities between the effects of synthetic caerulein, certainly free of GIP and other contaminated peptides,

Insulin and glucagon concentrations in portal and peripheral veins in patients with hepatic cirrhosis.

The portal vein was catheterized via the umbilical vein under local anaesthesia in 10 non-diabetic subjects about to undergo exploratory laparotomy and in 8 patients with liver cirrhosis. Immunoreactive insulin (IRI) and glucagon (IRG) were assayed in portal and peripheral blood before and during IV infusion of glucose (0.33 g/kg) or arginine (25 g). Basal peripheral plasma (IRI) levels were raised in cirrhotic patients (19±2 versus 10±1 μU/ml; P<0.001). Basal portal insulin values, however, did not differ in the two groups. After glucose cirrhotic patients had higher peripheral insulin concentrations, compared to controls, significant at 45 and 60 minutes. In contrast portal insulin levels were higher in controls than in cirrhotics by 1 minute (403±43 versus 158±38 μU/ml; P<0.001) and remained so for the 60 minutes of study. Similarly, after arginine cirrhotics had significantly higher peripheral insulin concentrations and lower portal concentrations than controls. Peak portal vein insulin levels were delayed in cirrhotics (168±16 μU/ml at 3 min) compared with controls (413±25 μU/ml at 1 min). In the basal state both portal and peripheral glucagon levels were higher in cirrhotics than control subjects. Unlike in controls, IV glucose did not suppress glucagon secretion in cirrhotic patients. Peripheral plasma glucagon concentrations after arginine were also consistently higher in cirrhotics than controls, but unlike insulin portal venous glucagon levels were also raised (1800±360 pg/ml, cirrhotics; 960±87 pg/ml, controls; P<0.001; 1 min after arginine infusion). We conclude that insulin secretion is decreased in liver cirrhosis and that the peripheral hyperinsulinaemia observed reflects diminished hormone metabolism. The high plasma glucagon levels observed in cirrhotic patients are the result of pancreatic hypersecretion of glucagon.

Effects of selective insulin or glucagon deficiency on glucose turnover.

To study the importance of glucagon and insulin in diabetes, somatostatin (ST) was infused, alone or with insulin or glucagon, in 11 conscious dogs. Plasma immunoreactive insulin (IRI) and glucagon (IRG) levels fell 65 +/- 4% and 33 +/- 3%, respectively, with somatostatin infusion. Glucose production (Ra) assessed by [3-3H]glucose, [2-3H]glucose, or [1-14C]glucose decreased transiently. This is in contrast to the rise in Ra seen after insulin withdrawal in depancreatized dogs, which have normal levels of IRG. Thus, suppression of IRG with somatostatin prevented an increase in Ra in spite of suppression of IRI. When near basal IRG levels were provided during ST infusion in normal dogs, Ra increased, indicating that glucagon contributes to the acute development of diabetes. When basal IRI levels were provided with ST, suppression of Ra was maintained, suggesting that the transience of the metabolic effects of ST-induced glucagon suppression requires concomitant insulin suppression. A comparison of glucose turnover measured using different tracers showed that ST-related hormonal changes did not alter the rate of futile cycling in the liver. ST induced a rise in plasma free fatty acid (FFA) levels, attributed solely to insulin deficiency, as glucagon suppression did not significantly alter FFA concentrations when normal insulin levels were maintained.

Effects of Histamine, of Histidine and of Anti-Histaminic Agents on the Release of Glucagon and Insulin from the Rat Pancreas

We have studied the effect of histamine (HA) and histidine (HIS) on the release of immunoreactive glucagon (IRG) and insulin (IRI) by isolated rat islets and pieces of pancreas. In isolated islets, HA and HIS stimulated IRG release at a glucose concentration of 3.0 mg/ml and IRI release at a glucose concentration of 0.5 mg/ml. In pieces of pancreas incubated in the presence of glucose (3.0 mg/ml), HA at a 2mM concentration stimulated IRG release and had no effect on the release of IRI; however, when the concentration of HA was doubled (4 mM), an inhibition of IRI release could also be demonstrated. HIS was ineffective. Perphenazine and dexchlorpheniramine, two anti-histaminic agents, inhibited IRG and stimulated IRI release. These results indicate that histamine, whether endogenous or exogenous, directly stimulated IRG and inhibits IRI release and suggest that some of the in vivo effects of histamine, such as hyperglycemia and lipid mobilization, may be mediated, at least in part, by these endocrinologic effects.

The Effect of the Intrapancreatic Calcium and Glucagon Administration on the Somatostain-Induced Inhibition of Insulin and Glucagon Secretion in Dogs

We made a study to determine if calcium and glucagon have an effect on insulin secretion, which is inhibited by somatostatin in normal dogs.After an over-night fast, six mongrel dogs weighing 15 to 32 kg were anesthetized with an intravenous administration of sodium pentobarbital.Calcium (0.8 mg/kg.b.w. of CaCl2) and glucagon (10-1 mg) were injected into the superior pancreaticoduodenal artery under the infusion of saline (1 ml/min) or cyclic somatostatin (50 μg bolus plus 5 μg/ml/min) through the pancreatic artery in 6 normal anesthetized dogs. Levels of plasma immunoreactive insulin (IRI) and glucagon (IRG) were estimated in the pancreatic vein and femoral artery by using the double antibody method and canine insulin standard and by employing anti-glucagon antibody AJ 15 (which crossreacted with glucagon-like immunoreactivity) and the method of dextran-coated charcoal. The saline and somatostatin infusions were conducted on the same dog at 20 minute intervals. Blood samples were collected from the pancreatic vein every 5 seconds for 2 minutes and thereafter every 1 min until 5 minutes had elapsed and from the femoral artery every 1 min.The results were the following : 1. The calcium levels of the pancreatic vein increased from 4 to more than 8 mEq/L within one minute, whereas those of the femoral artery did not change significantly. 2. Under the saline infusion, CaCl2 evoked a sharp rise in the pancreatic venous IRI levels which started 25 seconds after the injection, rose to a peak of thirteen folds from baseline at 40 seconds and lasted for almost 2 minutes, whereas under the somatostatin infusion, the peak level was reached at 55 seconds and affected only one third of those under the saline infusion. 3. IRG levels in the pancreatic vein under the saline infusion did not show any significant changes after the CaCl2 injection and were higher than those under the somatostatin infusion at all points. 4. Under the somatostatin infusion, 10-1 mg of glucagon did not induce any rise at all in IRI concentrations of the pancreatic vein. But when CaCl2 was given just before the glucagon administration, a slight but significant rise in IRI was observed.It is concluded that, in vivo, calcium has an insulin secretory effect under a normoglycemic state, and that somatostatin has an inhibitory action on both calcium- and cyclic-AMP-mediated insulin release.

Reflex adrenergic control of endocrine pancreas evoked by unloading of carotid baroreceptors in cats

The effects of unloading of the carotid baroreceptors on arterial plasma glucose concentration as well as on portal plasma immunoreactive glucagon (IRG) and insulin (IRI) concentrations were studied in anestethized, vagotomized cats either by sectioning the sinus nerves or by lowering the pressure in the isolated carotid sinuses. Complete elimination of the carotid baroreceptor discharge by cutting the sinus nerves caused an increase in the arterial plasma glucose concentration by 100% and an increase in the portal IRG level by about 200%, whereas the portal IRI concentration decreased to 50% of its basal value. These baroreceptor-induced changes of the plasma IRG and IRI levels seemed to be graded in relation to the drop in carotid blood pressure and they were clearly detectable when the pressure was lowered from 120 to 90 mmHg in the isolated carotid sinus preparation. The described reflex hyperglycemia, hyperglucagonemia and hypoinsulinemia were mediated to the pancreas and liver mainly by the sympatho-adrenal system, since cutting the splanchnic nerves above the adrenal glands abolished the hyperglycemia and hypoinsulinemic responses and markedly depressed the magnitude of the hyperglucagonemic response. In adrenalectomized cats, complete unloading of the baroreceptors evoked both hyperglucagonemia and hypoinsulinemia although the magnitude of the hormonal responses was diminished. In animals where the pancreas and liver were sympathectomized but the adrenal glands left intact, cutting the sinus nerves evoked a doubling of the IRG level and a slight increase in plasma glucose, but no significant change of the IRI level. I.v. infusion of adrenaline (1 microgram/kg X min) or noradrenaline (5 microgram/kg X min) caused pronounced increases in IRG and plasma glucose and a clear-cut reduction of IRI. We conclude that the function of the endocrine pancreas in the cat can be influenced by variations in the blood pressure by means of a reflex control which originates from arterial baroreceptors. This reflex adjustment of the endocrine pancreas is mediated chiefly by two links of the sympatho-adrenal system, namely by catecholamine-release from the adrenal medulla and, more importantly, by a direct adrenergic nerve fibre influence on the alpha- and beta- cells.

Adaptive changes in gluconeogenic enzymes in rat liver and kidney during long-term ethanol ingestion

Activities of three hepatic and renal gluconeogenic enzymes, phosphoenol-pyruvate carboxykinase (PEP carboxykinase), fructose-1, 6-diphosphatase (FD-Pase), glucose-6-phosphatase (G6Pase), together with plasma immunoreactive insulin (IRI) and glucagon (IRG) concentrations and the main parameters of carbohydrate metabolism, were measured in rats fed on liquid diets in which 36% of the total energy intake was derived from ethanol. Experiments were conducted both on medium fat and high fat (10% and 40% of total energy from fat respectively) diets. Two types of control diet were used, one in which ethanol was replaced by glucose (type I) and one (type II) in which it was replaced by glucose and fat in the same ratio as in the corresponding ethanol diet. PEP carboxykinase and FDPase showed statistically significant ethanol-induced increases (16%–40%) in both the medium fat and high fat diet groups, but the increases in hepatic G6Pase, although qualitatively similar, were not statistically significant. The renal enzyme activities increased to approximately the same extent, the increases varying from 3% to 40% in different groups. No statistically significant differences were found between the animals fed on the two types of control diet. No marked ethanol-induced changes were shown in plasma IRG concentrations, but plasma IRI concentrations tended to be lower in the groups receiving ethanol than in the control groups in both sets of experiments. The results show that the ethanol-induced inhibition of hepatic gluconeogenesis initiates compensatory mechanisms which, in long-term experiments, result in an increase in the maximum activity of the adaptive enzymes of gluconeogenesis both in liver and kidney, probably indicating regulation at the level of the tissue concentration of the enzyme protein. The similarity of the changes in the kidney and liver is suggestive of a common inductor for the gluconeogenic enzymes in both organs. The possible mediators of enzymic adaptation are discussed.