Glucagon Treatment Research Articles

Amino acid transport and turnover of a transport system in liver slices from rats treated with glucagon and antibiotics

Experiments have been conducted in which glucagon-induced stimulation of α-aminoisobutyric acid (AIB) transport in rat liver, presumably mediated by cyclic AMP, was markedly inhibited by actinomycin D, cycloheximide or puromycin. Inhibition of transport occurred despite the presence of high concentrations of cyclic AMP, suggesting that the nucleotide may act prior to, or at the same point as, the antibiotics. Kinetic studies showed that 1) the half-life of the glucagon-stimulated system(s) was less than 1 hour, and 2) glucagon treatment doubled V max without having any effect on the apparent K m for hepatic AIB transport. The results suggest that glucagon stimulates hepatic AIB transport by increasing the synthesis of some critical protein having a rapid turnover rate; this effect may be due to a prior increase in RNA synthesis.

Synergistic action of glucagon and insulin in regulation of hepatic regeneration

Rats eviscerated of portal splanchnic organs and deprived of a portal blood supply were maintained by continuous intravenous infusion; when given only electrolytes and glucose they were capable of a regenerative response to partial hepatectomy, as evidenced by a significant rise in the rate of hepatic DNA synthesis, but this response was delayed by about 24 hr and diminished by about two-thirds in comparison to normal controls. Addition of insulin (with glucose) or glucagon (with FreAmine) had little effect when given separately. In combination, however, the two hormones were capable of fully restoring the DNA biosynthetic rate to normal, even when the start of the hormone treatment was delayed for 6–7 hr after the partial hepatectomy. The modest but significant regenerative activity inducible in the near total absence of pancreatic hormones, and the non-deleterious effect of delaying insulin and glucagon treatment for 6–7 hr in eviscerated rats, both suggest that, despite the profound influence of these hormones, additional hormonal or humoral agents may be involved in the initial activation of hepatic regeneration. The precipitous fall in portal vein insulin levels to near zero that we observed during the first several hours of regeneration in normal (non-eviscerated) rats further supports this view, as does the preliminary finding that infusion of insulin and glucagon into eviscerated but non-hepatectomized control rats failed even minimally to excite DNA synthesis in intact livers. Thus, although there is a likelihood that other agents may serve to initiate and even to sustain regeneration, the pancreatic hormones, acting in synergy, appear to be the major regulators of the rate and possibly also of the magnitude of the proliferative process.

Effect of glucagon on phenylalanine metabolism and phenylalanine-degrading enzymes in the rat.

Glucagon administered subcutaneously to rats for 10 days had no significant effect on liver phenylalanine hydroxylase activity, but induced liver dihydropteridine reductase more than twofold. In rats administered a phenylalanine load orally, glucagon treatment stimulated oxidation and depressed urinary phenylalanine excretion. These responses could not be related to an effect of glucagon on hepatic tyrosine-alpha-oxoglutarate aminotransferase activity. Even in rats with phenylalanine hydroxylase activity depressed to 50% of control values by p-chlorophenylalanine administration, glucagon treatment increased the phenylalanine-oxidation rate substantially. Although hepatic phenylalanine-pyruvate aminotransferase was increased tenfold in glucagon-treated rats, glucagon treatment did not increase urinary excretion of phenylalanine transamination products by rats given a phenylalanine load. Glucagon treatment did not affect phenylalanine uptake by the gut or liver, or the liver content of phenylalanine hydroxylase cofactor. It is suggested that dihydropteridine reductase is the rate-limiting enzyme in phenylalanine degradation in the rat, and that glucagon may regulate the rate of oxidative phenylalanine metabolism in vivo by promoting indirectly the maintenance of the phenylalanine hydroxylase cofactor in its active, reduced state.

Experimental pancreatitis treated with glucagon or lactated Ringer solution.

One hundred twenty dogs were allocated randomly to five models of experimental pancreatitis and further assorted randomly within each model to four treatment groups. Pancreatitis models included the obstructed duodenal loop preparation and pancreatic duct injections of lactated Ringer solution or bile-trypsin solution at low or high pressures. Treatment groups were untreated controls; fluid-resuscitated animals; glucagon-treated animals; and animals that received both glucagon and fluids. Survival was recorded exactly up to 72 hours, at which time survivors were killed. Autopsy examinations recorded both gross and microscopic alterations in pancreatic structure. Glucagon treatment alone or in combination with volume resuscitation was not more efficacious than simple volume resuscitation in treatment of pancreatitis. In mild to moderate pancreatitis, glucagon therapy was associated with pancreatic hemorrhage not seen in either fluid-resuscitated or untreated control animals.

Glucagon treatment of muscular dystrophic mice: a lack of effect.

Nachweis, dass Körpergewicht, Dystrophie und Sterblickeit bei männlichen und weiblichen muskeldystrophischen Mäusen (dy/dy) nach 100tägiger Behandlung mit Glukagon (2 oder 10 μ g pro Tag, s.c.) unverändert blieben.

Observations on Glucagon Treatment in Pancreatitis

Fleischer, K. & Kasper, H. Observations on glucagon treatment in pancreatitis. Scand. J. Gastroent. 1974, 9, 371-376.Twenty-five patients with pancreatitis were treated with glucagon 6-12 mg daily over a period of from 3 to 12 days. Six patients received sustained-acting glucagon intramuscularly; in all the other patients the drug was given by infusion. In 80% of the patients abdominal symptoms were relieved while under glucagon, and a persistent fall in the serum lipase activity was noticeable in 68%. Glucagon therapy had to be stopped in 2 patients because of side-effects. The results are compared with those obtained in a group of patients with pancreatitis who did not receive glucagon.

Glucagon treatment for muscular dystrophy in the mouse.

Glucagon treatment for muscular dystrophy in the mouse.

Glucagon-Stimulated Phosphorylation of Mitochondrial and Lysosomal Membranes of Rat Liver In Vivo

The pancreatic hormone, glucagon, stimulates the net uptake of inorganic (32)P in vivo into rat liver and its incorporation into proteins of microsomes, mitochondrial membranes, and lysosomes. Incorporation into cytosolic proteins was enhanced only slightly by glucagon. More than 95% of the protein-bound phosphate is present as phosphoserine. Both the radioactivity and the total amount of protein-bound phosphate are increased after injection of glucagon. Glucagon treatment enhanced (32)P incorporation into the alcohol-ether soluble lipids of mitochondria but did not alter the relative distribution of (32)P in various phospholipid species.

Effect of glucagon and p-chlorophenylalanine on hepatic enzymes that metabolize phenylalanine

Injection of glucagon s.c. into rats caused about a fourfold increase in hepatic PPT. The maximum effect occurred 24 hr after a 0.3 mg/kg dose of glucagon, and increased enzyme activity persisted for 8 days after the single glucagon injection. The possibility that induction of PPT by glucagon might be clinically useful in human phenylketonuria, by providing an alternate pathway for removal of phenylalanine when it cannot be hydroxylated, was considered. Glucagon given to human phenylketonuric subjects did not cause detectable changes in the conversion of phenylalanine to phenylpyruvate, but the existence of increased hepatic PPT in these patients was not demonstrated. p-Chlorophenylalanine, an inhibitor of hepatic phenylalanine hydroxylase, caused in rats the following biochemical characteristics of human phenylketonuria: elevated plasma phenylalanine concentration, appearance of phenylpyruvate in plasma and in urine, and decreased rate of removal of a phenylalanine load. Glucagon given to rats treated with p-chlorophenylalanine induced PPT as in normal rats, but little or no change in phenylalanine metabolism in normal rats or in p-chlorophenylalanine-treated rats could be shown to result from PPT induction by glucagon. The functional significance of the increased PPT that occurs after glucagon treatment thus remains obscure.

Responses of mammalian histidine catabolic enzymes to dietary and hormonal treatments

1. 1. The effects of glucagon administration on hepatic histidase, urocanase, and histidine-pyruvate aminotransferase activities in vivo and interrelationships among a high protein intake, cortisol and glucagon in influencing the activities of these enzymes were studied. Histidine-pyruvate aminotransferase increased 30-fold in rats fed a 12% casein diet and injected subcutaneously with glucagon for 10 days, whereas histidase and urocanase increased only 3-fold and 2-fold, respectively. After withdrawal of glucagon, the aminotransferase decreased with an apparent half-life of 3.5 days. Kinetic analysis indicated that an increased rate of enzyme synthesis was responsible for the increases in enzymic activities. 2. 2. Histidine-pyruvate aminotransferase is also more responsive than histidase and urocanase in rats injected with cortisol and responded synergistically when glucagon and cortisol were administered together. The aminotransferase shows little response in rats fed a high protein diet. In contrast, histidase and urocanase are more responsive than the aminotransferase to induction by high protein feeding but respond only moderately in rats treated with cortisol or glucagon. Glucagon treatment seems to enhance the induction of histidase or urocanase by high protein feeding but the effect is less than additive.

The pentose phosphate pathway of glucose metabolism. Hormonal and dietary control of the oxidative nd non-oxidative reactions and related enzymes of the cycle in adipose tissue.

1. Measurements were made of the activities of the enzymes of the pentose phosphate pathway concerned in both the oxidative (glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase) and the non-oxidative (ribose 5-phosphate isomerase, ribulose 5-phosphate epimerase, transketolase and transaldolase) reactions of this pathway, together with hexokinase and phosphoglucose isomerase, in adipose tissue in a variety of nutritional and hormonal conditions. 2. Starvation for 2 days caused a significant decrease in the activities of all the enzymes of the pentose phosphate pathway, with the exception of glucose 6-phosphate dehydrogenase, when expressed as activity/2 fat-pads; only the activities of ribose 5-phosphate isomerase and ribulose 5-phosphate epimerase were significantly decreased on the basis of activity/mg. of protein. Re-feeding with a high-carbohydrate or high-fat diet for 3 days restored the activity of all the enzymes of the pentose phosphate pathway to the range of the control values, with the exception of transketolase, which showed a marked ;overshoot' in rats re-fed with carbohydrate. Starvation for 3 days caused a marked decrease in the activities of glucose 6-phosphate dehydrogenase and transketolase. 3. On the basis of activity/two fat-pads, alloxan-diabetes caused a marked decrease, to about half the control value, in the activities of all the enzymes concerned in the pentose phosphate pathway, transketolase showing the smallest decrease; hexokinase and phosphoglucose isomerase activities were also decreased. Treatment with insulin for 3 and 7 days raised the activities to normal or supranormal values, transketolase showing the most marked ;overshoot' effect. On the basis of activity/mg. of protein the activity of none of the enzymes was significantly decreased in alloxan-diabetes; transketolase and transaldolase activities were raised above the control values. With insulin treatment for 3 or 7 days the activities of all the enzymes were significantly increased, except that of ribulose 5-phosphate epimerase at the shorter time-interval. Glucagon treatment did not alter any of the enzyme activities expressed on either basis. 4. Thyroidectomy caused a decrease of 30-40% in the activities of enzymes of the pentose phosphate pathway, except for transketolase activity, which fell to 50% of the control value. Little change occurred in adipose-tissue weight or protein content. 5. Adrenalectomy caused a decrease of 40% in the activity of glucose 6-phosphate dehydrogenase and of 20-30% in the activities of the remaining enzymes of the pentose phosphate pathway; hexokinase activity was also decreased. Treatment with cortisone for 3 days did not significantly raise the activity from that found in adrenalectomized rats. Treatment of normal rats with high doses of cortisone had no significant effect on the activities of the enzymes of the pentose phosphate pathway in adipose tissue. 6. The changes in enzyme activities are discussed in relation to: (a) the concept of constant-proportion groups of enzymes; (b) the known changes in the flux of glucose through alternative metabolic pathways; (c) the pattern of change found in liver with similar hormonal and dietary conditions.

Effects of glucagon and fasting on acetate metabolism in perfused rat liver.

(1) Effects of glucagon treatment in vitro and of fasting on [2-14C]acetate metabolism were studied in perfused rat liver. Glucagon stimulated ketogenesis about 2.8 fold and the incorporation of label into ketone bodies only 1.7 fold. The diminished specific activity of ketone bodies produced in the presence of glucagon was interpreted as evidence for increased production and disposal (turnover) of acetyl-CoA. Inhibition of acetyl-CoA utilization by other routes, therefore, was not a major cause of the increased ketogenesis. From a consideration of label incorporation into derivatives of the Krebs cycle in relation to the specific activity of acetyl-CoA (as judged from ketogenic rate and label incorporated into ketone bodies) glucagon appeared to accelerate the initial steps of the Krebs cycle about 2 fold. It diminished label incorporation into fatty acids to a degree corresponding to the reduction in acetyl-CoA specific activity. Incorporation of label into cholesterol was not affected by glucagon. (2) In livers from fasting rats, ketogenesis was increased about 6.7 fold and label incorporation into ketone bodies was increased about 5.3 fold over values in fed controls. Thus, the turnover of acetyl-CoA appeard to be increased slightly by fasting. Krebs cycle activity was essentially unaffected by fasting. The inhibition of fatty acid and cholesterol synthesis in these livers appeared sufficient to contribute significantly to the ketogenic rate by sparing acetyl-CoA. (3) Gluconeogenesis from endogenous substrate was markedly stimulated by glucagon and moderately stimulated by fasting. (4) Secretion of newly synthesized total fatty acids, cholesterol and cholesterol ester into the circulation was markedly inhibited by glucagon.

Effects of prolonged glucagon administration to turtles ( Chrysemys d'Orbignyi)

Studies have been conducted on the action of glucagon upon carbohydrate metabolism of turtles ( Chrysemys d'orbignyi) during summer or winter. Daily administration of glucagon (100 μg/kg) for 30 days produced intense hyperglycemia, this effect being greater during winter than in summer. Also, the effect in winter decreased as the experiment proceeded. Blood glucose reached normal levels 20 days after suspension of glucagon treatment. At the end of experiment, the liver glycogen concentration of the treated turtles was lower than in the controls. Muscle glycogen values were not changed by glucagon injections. Plasma insulin-like activity from the treated animals was increased. Pancreas insulin content from the treated animals did not present appreciable modification during the summer, but it was reduced in experiments performed during the winter.

THE EFFECT OF DIFFERENT HORMONAL CONDITIONS ON THE CONCENTRATION AND OXIDOREDUCTION STATE OF THE NICOTINAMIDE NUCLEOTIDES OF RAT LIVER.

1. The concentration and oxidoreduction state of the liver nicotinamide nucleotides of rats subjected to a number of hormonal treatments have been measured. 2. Adrenalectomy decreases the NADP(+) content by 80% but has little effect on NAD(+), NADH or NADPH. High doses of cortisone produce similar changes, but more physiological doses (5mug. daily) tend to increase the NADP(+) content. 3. Glucagon treatment of normal rats lowered the NADH and NADP(+) concentrations but did not affect the total amounts present. Growth hormone increased the concentrations and total amounts of NAD(+) and NADH but significantly decreased the concentrations and total amounts of NADP(+) and NADPH. 4. Measurements have been made of a number of enzymes in the livers of adrenalectomized and glucagon-treated rats that could affect the oxidoreduction state of NADP. The activities of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase are not affected by adrenalectomy or treatment with cortisone or glucagon. Nor does adrenalectomy affect the activity of NADPH-cytochrome c oxidoreductase or NADPH-glutathione oxidoreductase. The hepatic content of glutathione is, however, decreased 50% by adrenalectomy. 5. Measurements of the oxidation of [1-(14)C]glucose and [6-(14)C]glucose by liver slices from adrenalectomized rats showed that glucose oxidation was substantially normal, although phenazine methosulphate caused a smaller stimulation of the oxidation of C-1 of [1-(14)C]glucose in slices from the livers of adrenalectomized rats than it did with slices from controls. The hepatic synthesis of lipids from [1-(14)C]glucose was marginally increased in adrenalectomized rats. 6. The additional NADP(+) found when liver is extracted with 0.02n-sulphuric acid-0.1m-sodium sulphate is less affected than the NADP(+) extracted with 0.1n-hydrochloric acid in adrenalectomized or glucagon-treated rats. Hooded Norway rats appear to have less of this extra form of NADP(+) than albino rats. 7. An attempt has been made to correlate the observed changes in the nicotinamide nucleotides with metabolic patterns prevailing in different hormonal conditions.

EFFECTS OF LONG TERM ADMINISTRATION OF GLUCAGON ON THE PANCREATIC ISLET TISSUE OF RATS AND GUINEA-PIGS.

ABSTRACT Rats and guinea-pigs were injected every eight hours with crystalline glucagon (0.3–0.6 mg/kg) and killed after different periods of treatment up to 30 days. Immature animals (glucagon treatment commenced on the second postnatal day) were also included among the rats investigated. While the immature glucagon treated rats grew almost as well as their litter mate controls, there was a marked reduction of the body and adrenal weights, when the injections were started at a more adult age. In the latter rats the total islet volume was significantly reduced and the A1/A2 cell number ratio increased from 0.24 ± 0.02 to 0.32 ± 0.02. In the guinea-pigs the glucagon treatment resulted in a considerable decrease in both the body and pancreatic weights. These changes were associated with a significant increase in the relative amount of the endocrine pancreas, the total islet volume being unchanged. While the A1 cells appeared unaffected by the glucagon treatment, the A2 cells were markedly atrophied. After an apparent initial increase there was a subsequent progressive diminution of the silvery-white dark field granulation of the A2 cells during the glucagon treatment. The postcoupled benzylidene reaction for tryptophane also decreased and became insignificant in guineapigs injected with glucagon for a long period. In the latter animals the percentage of A2 cells was only 3.4 ± 0.2 as compared with 24.4 ± 1.3 for the controls. As a consequence of this, the A1/A2 cell number ratio was about 6 times as high in the glucagon treated guinea-pigs. The data obtained for the longer term adaptation of the islets of Langerhans to the administration of glucagon support the concept that this hormone is secreted by the silver-negative A2 cells.

Insulin-like activity of crystalline glucagon as measured with rat epididymal fat pad preparation.

SummaryA small amount of insulin-like activity has been found in crystalline preparations of glucagon with rat epididymal fat pad preparation. Treatment of glucagon with cysteine lowers this insulin-like activity to a small fraction of initial activity.

"Metaglucagon diabetes" in rabbits.

IT has been shown in this and other laboratories that the administration of glucagon will produce an intense but temporary diabetes in force-fed rats and in human subjects.1 2 3 However, a diabetes persisting after cessation of glucagon treatment has not been reported in any species. This paper is a preliminary account of investigations yielding evidence that when immature rabbits are treated with glucagon for a prolonged period a "metaglucagon diabetes" can be produced.Methods and ProceduresThe litters of three albino rabbits of mixed origin were used. Treatment was started on the third postnatal day. Nine of the animals received a . . .

Glucagon treatment of insulin reactions.

PREVIOUS studies have shown that glucagon is capable of counteracting the hypoglycemic effect of insulin in normal man,1 in psychotic patients undergoing insulin-coma therapy2 and in diabetic patients.3 In this paper evidence is presented that glucagon is an effective agent for the treatment of insulin reactions in diabetic patients. Experimental Data Patients Eighteen hospitalized male diabetic patients, thirty to sixty-nine years of age, were studied. The known duration of the diabetes in the group ranged from one to twenty-five years. All patients required insulin; the daily requirement ranged from 12 to 150 units. All had a history of previous insulin . . .