Is glucagon involved in cold acclimatization?

Cold acclimatization in rats at 5 degrees C for 2 weeks caused a significant elevation of plasma glucagon concentration, accompanied by increased plasma FFA and glucose levels. Acute cold exposure at 5 degrees C for 5 or 60 min did not affect these parameters in plasma.     

Independence of circulating insulin levels of the increased glucose turnover in shivering dogs

Summary In dogs, selective insulin deficiency induced by simultaneous somatostatin and glucagon infusion does not alter the high rate of glucose utilization provoked by acute cold exposure. However, both in resting and in shivering dogs, lowering of plasma insulin decreases plasma glucose metabolic clearance significantly.     

Independence of circulating insulin levels of the increased glucose turnover in shivering dogs

In dogs, selective insulin deficiency induced by simultaneous somatostatin and glucagon infusion does not alter the high rate of glucose utilization provoked by acute cold exposure. However, both in resting and in shivering dogs, lowering of plasma insulin decreases plasma glucose metabolic clearance significantly.     

Is glucagon involved in cold acclimatization?

Summary Cold acclimatization in rats at 5°C for 2 weeks caused a significant elevation of plasma glucagon concentration, accompanied by increased plasma FFA and glucose levels. Acute cold exposure at 5°C for 5 or 60 min did not affect these parameters in plasma.We are grateful to Drs.H. Ohhara andA. Kihara, Sapporo Medical College, for help in setting up glucagon radioimmunoassay.     

Endocrine and exocrine pancreatic function after camostate-induced growth of the organ

It is well known that oral administration of camostate induces hyperplasia and hypertrophy of the rat pancreas. It is not clear, however, whether pancreatic hormone and enzyme secretion are affected by camostate treatment.In rats, daily administration of 200 mg camostate/kg b. wt for 14 days significantly increased pancreatic weight and pancreatic content of DNA, protein, amylase, lipase, trypsin and chymotrypsin, as well as the amount of insulin, glucagon and somatostatin. In the intact animal, blood glucose levels and serum concentrations of insulin and glucagon in response to an oral glucose load were not impaired after camostate treatment. In the isolated perfused pancreas, however, insulin and glucagon secretions were reduced, whereas somatostatin release was not affected. The volume of pancreatic juice produced by the unstimulated isolated perfused organ, as well as protein and enzyme secretion, were increased after camostate treatment. Likewise, the isolated perfused pancreas from camostate-treated rats secreted a larger volume of pancreatic juice and more protein in response to cholecystokinin (CCK), while enzyme secretion was affected in a non-parallel manner: amylase release was markedly reduced, lipase release was unchanged, and release of trypsin and chymotrypsin was increased.     

Stimulation of glucagon and inhibition of insulin secretion evoked from carotid baroreceptors

Summary The influence from carotid baroreceptors on portal immuno-reactive glucagon and insulin levels and on arterial plasma glucose concentration was studied in vagotomized cats by sectioning of the sinus nerves. Such a complete elimination of the afferent baroreceptor discharge caused a prompt and pronounced increase in the glucose and glucagon levels, whereas the insulin concentration significantly decreased. The role of vascular baroreceptors in the hyperglycemic response to hemorrhage is discussed.     

Stimulation of glucagon and inhibition of insulin secretion evoked from carotid baroreceptors.

The influence from carotid baroreceptors on portal immuno-reactive glucagon and insulin levels and on arterial plasma glucose concentration was studied in vagotomized cats by sectioning of the sinus nerves. Such a complete elimination of the afferent baroreceptor discharge caused a prompt and pronounced increase in the glucose and glucagon levels, whereas the insulin concentration significantly decreased. The role of vascular barorecptors in the hyperglycemic response to hemorrhage is discussed.     

Effect of long acting somatostatin-analogue, SMS 201 995, on gut hormone secretion in normal subjects

SMS 201 995 is a new long acting analogue of somatostatin. We have investigated its effect on basal and meal stimulated secretion of gut hormones and have shown that after a single s.c. injection of 50 micrograms it lowers significantly the basal plasma levels of pancreatic polypeptide, secretin, motilin, pancreatic glucagon and insulin, it also effectively suppresses the postprandial release of pancreatic polypeptide, gastrin, secretin, gastric inhibitory peptide, pancreatic glucagon and insulin. Except for the usual brief discomfort of an injection, no symptoms or untoward effects were observed.     

Effect of long acting somatostatin-analogue,SMS 201995, on gut hormone secretion in normal subjects

Summary SMS 201 995 is a new long acting analogue of somatostatin. We have investigated its effect on basal and meal stimulated secretion of gut hormones and have shown that after a single s. c. injection of 50 g it lowers significantly the basal plasma levels of pancreatic polypeptide, secretin, motilin, pancreatic glucagon and insulin, it also effectively suppresses the postprandial release of pancreatic polypeptide, gastrin, secretin, gastric inhibitory peptide, pancreatic glucagon and insulin. Except for the usual brief discomfort of an injection, no symptoms or untoward effects were observed.     

Effect of glucagon on ethanol oxidation in isolated rat liver cells

Summary Addition of glucagon 5 min after ethanol was found to stimulate the rate of ethanol oxidation in hepatocytes isolated from starved rats. This stimulation is of the same order of magnitude as that mediated by asparagine. The glucagon effect is suppressed by antiproteolytic agents such as insulin or NH₄Cl. The stimulatingeffect of glucagon on ethanol oxidation is probably liked to enhanced proteolysis andan elevated glutamate level in the hepatocytes.Acknowledgments. this investigation was supported by grants from the Institut de la Santé de la Recherche Médicale, the Scientific Council of the Faculté de Médecine Paris-Ouest and the Ecole Pratique des Hautes Etudes (3rd section).     

Acute cold exposure increases the glucagon sensitivity of thermogenic metabolism in the rat

Administration of glucagon to rats at 25 degrees C had no effect upon their VO2, while administration of noradrenaline or noradrenaline plus glucagon raised the VO2. At 5 degrees C, noradrenaline had no effect upon the cold-enhanced VO2, while glucagon caused a rise of 13.7%, implying increased glucagon sensitivity at 5 degrees C. The glucagon-induced enhancement of VO2 was abolished by concurrent administration of noradrenaline.     

The glucose dependence of pancreatic endocrine responses to 2-deoxyglucose in the calf

Summary The initial plasma glucose concentration of unanesthetized calves with cut splanchnic nerves, given 2-deoxyglucose (1.2 mmoles/kg, i.v.), was either lowered by prior starvation, or raised by a continuous infusion of exogenous glucose. Raising the initial plasma glucose concentration completely suppressed the release of pancreatic glucagon and pancreatic polypeptide but substantially enhanced the release of insulin in response to 2-deoxyglucose.This work has been supported by the Medical Research Council and the Leverhulme Trust. We are also indebted to Mr P.M.M. Bircham and Mr G.P. Macgregor for their skilled technical assistance.     

Effects of insulin on plasma fibrinogen levels in rats submitted to tissue injury or ACTH administration.

Insulin is necessary to produce an increase of plasma fibrinogen in rats submitted to tissue injury or ACTH administration. This increase is more significant when endogenous or exogenous excess of insulin is present, while in uninjured rats the absence or excess insulin does not modify plasma fibrinogen.     

Effects of insulin on plasma fibrinogen levels in rats submitted to tissue injury or ACTH administration

Summary Insulin is necessary to produce an increase of plasma fibrinogen in rats submitted to tissue injury or ACTH administration. This increase is more significant when endogenous or exogeneous excess of insulin is present, while in uninjured rats the absence or excess of insulin does not modify plasma fibrinogen.     

Acute cold exposure increases the glucagon sensitivity of thermogenic metabolism in the rat

Summary Administration of glucagon to rats at 25°C had no effect upon their VO₂ while administration of noradrenaline or noradrenaline plus glucagon raised the VO₂-At 5°C, noradrenaline had no effect upon the cold-enhanced VO₂, while glucagon caused a rise of 13.7% implying increased glucagon sensitivity at 5°C. The glucagon-induced enhancement of VO₂ was abolished by concurrent administration of noradrenaline.     

Effects of glucagon and insulin on the Paneth cells of the mouse duodenum.

The effect of glucagon and insulin on the paneth cells (PC) of the duodenum of the mouse was investigated using light microscopy. Both glucagon and insulin were able to increase significantly the number of the secretory granules of PC. This possibly means that these hormones are capable of inhibiting the secretion of PC.     

Secretion of insulin and of glucagon by the perfused pancreas of newborn rats: effect of vasoactive intestinal peptide Vip]

A method is described for perifusion of the splenic part of the pancreas from 48-64 hour-old rat. In different basal conditions, the secretion of insulin and glucagon is stable and reproducible for 90 mn. The addition of the vasoactive intestinal peptide (VIP) to these perifusion media, at a concentration as low as 2 ng/ml, determines a remarkable increase of insulin and of glucagon secretion. These results suggest the possibility of a VIP action in the physiology of endocrine pancreas.     

Establishment of serum based essentiall free of proteolytic activity for the culture of mouse pancreatic islets.

The present study demonstrates that a) serum based culture medium degrades 125I inhibits its proteolytic activity leading to the recovery of more insulin secreted by islets cultured in the presence of high glucose concentration alone or with glucagon; c) aprotinin also favoured the accumulation of secreted insulin by protecting the hormone from a residual degradative capacity of the hear treated serum.     

Glucagon receptors

Glucagon is a pancreatic peptide hormone that, as a counterregulatory hormone for insulin, stimulates glucose release by the liver and maintains glucose homeostasis. First described as a glucagon binding entity functionally linked to adenylyl cyclase, the glucagon receptor is a member of the family B receptors within the G protein coupled superfamily of seven transmembrane-spanning receptors. During the past decade, considerable progress has been made in the identification of the molecular determinants of the glucagon receptor that are important for ligand binding and signal transduction, in the development of glucagon analogs and of nonpeptide small molecules acting as receptor antagonists, and in the characterization of the mechanisms involved in the regulation of expression of the glucagon receptor gene. In the present review, the current knowledge of glucagon receptor structure, function and expression is described, with emphasis on the metabolic fate of glucagon and on the endocytosis and cell itinerary of both ligand and receptor.     

Effect of the glucagon on the plasma insulin-activity after hypophysectomy

Résumé La disparition de l'effet insulinique du plasma que l'on observe après l'hypophysectomie n'a pas lieu quand les animaux (rats) ont été préalablement soumis à un traitement de glucagon (0,5 mg suspendu en Bayol F).