Alloxan Diabetic Animals Research Articles

Effect of blood sugar levels on glycogen content of hypophysis and adrenal glands.

SummaryGlycogen content of the components of hypophysis and adrenal glands is determined. In the normal rat, neurohypophy-sis contains more glycogen than does the adenohypophysis (439 vs 298 μg per 100 mg dry weight of tissue). In the alloxan-diabetic animals, the medullary glycogen content was greatly elevated. Hyperglycemia produced by glucose injection caused little change in the glycogen content of neuro- and adenohypophysis and also in the adrenal medulla, but significantly decreased that of the adrenal cortex. Fall in blood sugar levels (insulin injection) decreases the glycogen content of all the components of the hypophysis and adrenal glands. Perhaps the changes in glycogen content are related to hormonal synthesis and secretion. Although injection of ACTH causes a 27% decrease in the glycogen content of the normal rat adrenal cortex at 2 and 4 hours, no significant decrease was found in the diabetic animals at these time periods.

Die Beteiligung des Insulins an der Diazoxid-Hyperglyk�mie

Insulin deficiency in alloxan diabetic animals has been shown to reduce the active form of glycogen synthetase. This enzymic impairment has also been found in diazoxide treated rats. The conclusion that diazoxide lowers insulin incretion has been proved by measuring the radioimmunologically detectable insulin plasma concentration.

Der Einflu� von Insulin auf den Kaliumtransport in der Skeletmuskulatur

The ability of insulin to increase the l-arabinose distribution volume in alloxan diabetic rats has been found decreased in 6-aminonicotinamide (6-AN) treated rats. The percentage decrease is equal to the impairment in the insulin dependent glucose transport. From this it has been concluded that the 6-AN induced impairment of the glucose diffusion facilitated by insulin is localized in the cellular membrane. Insulin plasma concentration has been found increased in 6-AN treated animals in response to an accelerated glycogenolysis mediated by an increase in epinephrine secretion. The increase in insulin secretion has been shown to cause an activation in potassium transport in skeletal muscle. Alloxan diabetic animals do not exhibit the stimulation in net cellular potassium uptake nor do adrenalectomized rats the plasma insulin concentration of which does not rise because of the lack in epinephrine mediated glycogenolysis. With especially high rates of epinephrine induced glycogenolysis plasma insulin concentration has been found to increase to a smaller degree than would be expected from the blood glucose concentration of these animals. In accordance to the results published byCoore andRandle (1964) andPorte, Graber, Kuzuya, andWilliams (1966) it is assumed that higher concentrations of epinephrine are capable to suppress insulin secretion in spite of an increase in blood glucose concentration.

Evidence for the presence of two types of pyruvate kinase in rat liver

Two types of pyruvate kinase were identified by electrophoresis and an immunological procedure and tentatively named type L and M. Type M is distributed in muscle, brain, heart, liver and kidney, having the same nature in all these organs. Type L, which was not neutralized with anti-type M serum, was only found in liver and kidney. Anti-serum for type M was used in estimating the levels of the two types of enzyme in tissue extracts. The level of type L varied greatly under various physiological conditions, whereas that of type M only changed slightly. In alloxan diabetic animals and those fed on a high protein diet or fasted for 48 hours, the total level of pyruvate kinase as well as the ratio of type L to type M were greatly decreased, and on subsequent insulin administration or administration of a normal diet the levels returned to normal. On the basis of comparative studies on the two types of pyruvate kinase in regenerating liver and tumor cells, the possibility that the control mechanism might depend on the stage of differentiation of the enzyme was discussed.

Protein synthesis by ribosomes from heart muscle: effect of insulin and diabetes.

Incorporation of phenylalanine into protein by ribosomes from the heart muscle of rats is decreased when the ribosomes are from alloxan-diabetic animals. Protein synthesis is increased when the ribosomes are obtained from nondiabetic animals I hour after treatment with insulin. The change due to insulin appears to be an alteration in the function of the ribosome.

The metabolism of the retina of the normal and alloxan diabetic rat The levels of oxidised and reduced pyridine nucleotides and the oxidation of the carbon-1 and carbon-6 of glucose

The levels of oxidised and reduced NAD and NADP have been determined in the retinae of normal and alloxan-diabetic rats. In the alloxan-diabetic animal the ratios of NAD/NADH2 and of NADPH2/NADP are both reduced, as a result of an increase of NADH2 and a decrease of NADPH2. The relative rates of oxidation of the carbon-1 and carbon-6 of glucose have been studied using C-14 labelled glucose. A C-1/C-6 ratio of 1.13 was obtained for both normal and alloxan-diabetic animals. The levels of the oxidised and reduced co-enzymes in the retina of the normal rat are similar to those of brain and contrast with those of liver; this would suggest a minimum activity for the pentose phosphate pathway. This idea is supported by the ratio of oxidation of C-1/C-6. The co-enzyme changes in the retina of the alloxan-diabetic rat could be taken to infer an increased glycolytic rate, but a reduced rate of breakdown by the shunt mechanism. This possibility is not reflected in the C-1/C-6 ratios. The factors that complicate these interpretations are discussed.

Effect of insulin on pyruvate carboxylase in alloxan diabetic animals

Effect of insulin on pyruvate carboxylase in alloxan diabetic animals

Induced biosynthesis of liver glucokinase

A glucokinase qualitatively and quantitatively adequate as the first and limiting step in the synthesis of glycogen from glucose in liver has recently been identified in normal fed rats. In contrast with hexokinase, that also occurs in liver, glucokinase activity disappears in fasted and alloxandiabetic animals. The high Km, glucose-6-P-insensitive glucokinase, does not occur in muscle, nor in any of several other tissues examined. This and other indirect evidence suggest that the glucokinase is a unique enzyme of the parenchymal cells of the liver, and that the hexokinase measured in liver homogenates is present in the non-parenchymal cells. Glucokinase reappears in diabetic and fasted animals within a few hours after administration of insulin or refeeding respectively. Glucose administration alone is also effective in provoking the reappearance of glucokinase activity in previously fasted rats. Liver hexokinase remains essentially unaltered in these conditions. Inhibition of the reappearance of glucokinase by ethionine and p-fluorophenylalanine, largely counteracted by methionine and phenylalanine respectively, suggests that actual synthesis of the enzyme is involved. A similar effect of actinomycin supports this conclusion while it further suggests that formation of messenger RNA is involved. These results suggest that liver glucokinase is an inducible enzyme whose synthesis is induced directly or indirectly, by insulin. The differences in the hexosemonophosphate pathway between liver and muscle, their metabolic regulation, and the relationship with other pathways is discussed.

Studies on pyruvate carboxylase activity in alloxan diabetic and normal animals

Studies on pyruvate carboxylase activity in alloxan diabetic and normal animals

Hypoglycemic Activity of 3,5 Dimethylisoxazole

Summary3, 5 dimethylisoxazole (U-21221) was found to be 188 times more potent orally than tolbutamide in glucose-primed fasted intact rats. U-21221 also increased glucose oxidation by intact rats. It did not lower blood sugar of eviscerate rats but was active in alloxan diabetic animals which were unresponsive to tolbutamide. It was suggested that the mechanism of action of 3,5 dimethylisoxazole was by stimulation of glucose oxidation by the gut and/or liver.

Studies on carbon dioxide fixation in normal and alloxan-diabetic animals

Studies on carbon dioxide fixation in normal and alloxan-diabetic animals

Changes in the ascorbic acid and glutathione content of the retinae and adrenals from alloxan-diabetic rats

Reduced and oxidized glutathione and ascorbic acid were determined in the retinae and adrenals from normal and alloxan-diabetic rats. In the retina, there was a statistically significant decrease in the total glutathione but no significant change in the total ascorbic acid. In the adrenals a statistically significant increase in reduced ascorbic acid and a decrease in oxidized glutathione were observed; the increase in total ascorbic acid was also significant in the alloxan-diabetic animals. The increase in weight of the adrenals from the diabetic rat was statistically significant but no change in the weight of the retinae was observed. These results are in agreement with the known adrenal hyperplasia that occurs in diabetes but would indicate that swelling of the retina due to imbibition of water had not taken place.

Glycogen in the uterus of alloxan-diabetic rats.

The effect of estrogen on the concentration of glycogen was determined in tissue samples from the uterus, liver, diaphragm and urinary bladder of spayed, alloxan-diabetic rats. Uterine glycogen was significantly increased in the alloxan-diabetic animals. Furthermore, uterine glycogen was significantly higher in the estrogen-treated alloxan-diabetic rats than it was after either alloxan treatment or estrogen treatment alone. These increases appeared to be related to the elevated blood sugar. The glycogen content of the urinary bladder was not altered.

Metabolism of C14-labeled substrates in kidney cortical slices from normal and alloxan-diabetic rats.

The metabolism of C14-labeled glucose, fructose, mannose and pyruvate was studied in kidney slices from normal and alloxan-diabetic rats. Labeled carbon was recovered in CO2, glycogen and fatty acids. The rate of mannose metabolism was consistently slightly less than that of glucose, and on the other hand, the rate of fructose metabolism was consistently greater. In slices from alloxan-diabetic animals the metabolism of glucose and mannose was markedly reduced; that of fructose was only slightly decreased. No effect of insulin added in vitro could be demonstrated on glucose metabolism. Pyruvate oxidation to CO2 was slightly increased in slices from diabetic animals. Furthermore, glucose production was increased sixfold by diabetes and, as calculated, 75% of this glucose production could be accounted for by glucose synthesized from labeled pyruvate. The similarity between carbohydrate metabolism in liver and kidney was pointed out.

Effects of glucose on fatty acid oxidation by diaphragms from normal and alloxan-diabetic fed and starved rats.

Palmitic acid-1-C14 oxidation by hemidiaphragms was measured in tissues from fed and starved normal and alloxanized rats. Muscle from normal rats starved for 3 days or longer showed an enhanced conversion of added palmitate to C14O2, while fasting for 1 or 2 days had little effect on fatty acid degradation by diaphragms from normal rats. Tissues from fed or starved alloxan diabetic animals had an augmented oxidation of labeled palmitate. The addition of glucose to the medium spared fatty acid oxidation by diaphragms from starved or diabetic rats but did not influence palmitate degradation by tissues from normal fed rats. The presence of insulin increased the glucose sparing action on long-chain fatty acid oxidation but was without effect on palmitate oxidation in the absence of added glucose. The conversion of C14-octanoic acid to C14O2 by muscle was not influenced by previous starvation nor by addition of glucose to the medium. Glucose-U-C14 and glucose-1-C14 conversion to C14O2 and glycogen were essentially the same in diaphragms from fed and starved animals.

Clinical trials with DBI, a new nonsulfonylurea oral hypoglycemic agent.

The current medical literature contains many reports of studies with oral hypoglycemic agents.^1-3These substances thus far have been sulfonylurea derivatives with blood-sugar-lowering ability in certain types of diabetes. Within the last year studies were started with a new group of compounds classified as formamidinyliminoureas. These drugs are biguanides, not to be confused with the diguanidines, which include Synthalin (guanidine-deca-methylene-guanidine) (Fig. 1). They also have no structural relationship to either carbutamide or tolbutamide and have no sulfonyl radical in their formulae. Ungar et al.⁴recently reported that one of these agents, phenethylformamidinyliminourea hydrochloride, was effective orally in both normal and alloxandiabetic animals. He also reported⁵the uptake of glucose by a rat diaphragm preparation. Williams⁶reported a hypoglycemic effect in animals, and Nielsen et al.⁷stated that this hypoglycemic effect was observed in depancreatized animals. Pomeranze⁸first demonstrated successful hypoglycemic effects in clinical trials with patients. This present report is

THE ISLETS OF LANGERHANS IN PANCREATIC FIBROSIS

A survey is given of earlier views on the occurrence of diabetes and decreased glucose tolerance in cystic fibrosis of the pancreas, as well as on the structure of the islet tissue in this disease and in experimental fibrosis of the pancreas. Intravenous glucose tolerance tests were performed in three patients with cystic fibrosis. of the pancreas, and normal glucose tolerance curves obtained. Fibrosis of the pancreas was produced experimentally in rabbits by ligation of the pancreatic duct. In eight of nine such animals, the glucose tolerance was normal. Histologically, the pancreas exhibited total acinar atrophy, with cystic dilatation of the ducts, between which numerous small islets of Langerhans of fetal type were compressed. The general picture was similar to that seen in the fetus and in cystic fibrosis of the pancreas. Quantitative determinations of the islet volume showed a great reduction in size of the islet tissue, due chiefly to a marked decrease in area of the individual islets. The alpha-to-beta cell relations were, however, normal. The results are discussed, and compared with those in alloxan-diabetic animals and with animals with experimentally produced hypertrophy of the pancreas. In the latter the islet tissue hypertrophies as well (Fig. 7). The prenatal relations between the exocrine and endocrine tissues of the pancreas may also exist postnatally. The resistance to the diabetogenic effect of alloxan present in animals with the pancreatic duct ligated seems to be associated with the immature, fetal structure of the islet tissue in acinar fibrosis.

Effects of niacin and vitamin C on blood sugar.

Intramuscular injection of niacin in normal rats induces hyperglycemia which lasts approximately 1 hour. In adrenalectomized rats niacin produces a hypoglycemia. Subcutaneous injection of vitamin C lowers blood sugar in normal and diabetic rabbits, the effect being pronounced when the blood level of vitamin C is high. The simultaneous administration of niacin and vitamin C produced a pronounced hypoglycemia. The rise in blood sugar normally produced by niacin is nullified if vitamin C is injected simultaneously or shortly thereafter. In both normal and diabetic animals, vitamin C injections produce an increase in liver glycogen. The vitamin C content of liver is lower in normal than in alloxan diabetic animals.

Factors determining the liver glycogenating action of orinase.

The liver glycogenating action of Orinase was studied in normal, adrenalectomized and alloxan diabetic rats. The adrenalectomized rats were studied in three groups, salt maintained, cortisone maintained and cortisone plus adrenaline maintained. The alloxan diabetic rats were studied in two groups, protamine zinc insulin (P.Z.I.) maintained and uncontrolled. Of the adrenalectomized rats only those maintained on cortisone plus adrenaline responded to Orinase administration with increased liver glycogen. The alloxan diabetic animal maintained on P.Z.I. presented increased liver glycogen after Orinase administration but the untreated alloxan diabetic rat did not. This series of experiments indicated that the liver glycogenating effect seen during Orinase administration requires the participation of adrenomedullary, adrenocortical and beta cell hormones.

β-Hydroxybutyric Dehydrogenase Activity in Alloxan Diabetic Animals

As I previously reported, urinary content of ketone bodies reflects the condition of diabetes mellitus fairly precisely. Ketone Wiles consist of acetoacetic acid, β-hydroxybutyric acid and acetone. In diabetic ketosis, it was found that the percentage of these components was different from that in normal adults. In order to ellucidate the metabolic change in diabetes mellitus more precisely, β-hydroxybutyric dehydrogenase activity was measured in heart muscle, liver and kidney of the alloxan diabetic animals and following results were obtained.I. In alloxan diabetic animals, tissue β-hydroxybutyric dehydrogenase activity was found to be decreased compared with normal animals. This decrease was marked especially in liver.2. After treatment using insulin and mesoxalate this activity was normalized,. while PEDG was ineffective.3. Pantothenic acid and nicotinamide treatment caused slight increase in the activity of this enzyme.4. Sulfonylurea treatment caused decrease in β-hydroxybutyric dehydrogenase activity.