EFFECT OF PITUITARY EXTRACTS UPON GLUCOSE UPTAKE BY DIAPHRAGMS FROM NORMAL, HYPOPHYSECTOMIZED, AND HYPOPHYSECTOMIZED-ADRENALECTOMIZED RATS

ABSTRACT Hemidiaphragms of adrenalectomized rats which had been nembutalized prior to decapitation, were incubated under aerobic conditions and the glucose uptake and glycogen deposition were measured. Addition of adrenaline in vitro induced marked glycogen degradation and a relative small decrease in glucose uptake. Pretreatment with adrenaline in vivo, however, appeared to increase glycogen deposition in vitro while glucose uptake increased to an equivalent extent. This effect was attributed to the low initial glycogen content induced by this treatment. Double exposure to adrenaline by administering this substance both in vivo and in vitro, neither affected glucose uptake nor glycogen deposition as compared with untreated control diaphragms. However, there was a significant difference in the glycogen level at which both groups metabolized, this level being extremely low in diaphragms doubly exposed to adrenaline. It was concluded that the action of adrenaline on muscular carbohydrate metabolism consists basically of three different stages: 1. A temporary initial stage during which glucose assimilation is inhibited secondarily to glycogen degradation. 2. A second stage, in which the occurrence of inhibition of glucose assimilation is determined by the fact whether in the corresponding control tissue the glucose uptake is raised in favour of glycogen deposition. 3. A stage of recovery induced by discontinuing the exposure to adrenaline. This stage is characterized by glycogen deposition and an equivalent rise in glucose assimilation.

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EFFECTS OF ADRENALINE ON CARBOHYDRATE METABOLISM IN THE ISOLATED DIAPHRAGM OF INTACT AND ADRENALECTOMIZED RATS AS INFLUENCED BY »NEMBUTAL« ANAESTHESIA

Acta Endocrinologica ◽

10.1530/acta.0.xxxv0541 ◽

1960 ◽

Vol XXXV (IV) ◽

pp. 541-550 ◽

Cited By ~ 7

Author(s):

P. R. Bouman ◽

W. Dermer

Keyword(s):

Glucose Uptake ◽

Carbohydrate Metabolism ◽

Glycogen Content ◽

Glycogen Metabolism ◽

Rat Diaphragm ◽

Simultaneous Inhibition ◽

Glycogen Deposition ◽

Isolated Rat ◽

Adrenalectomized Rats

ABSTRACT Hemidiaphragms of intact and adrenalectomized rats which had been killed by decapitation, were incubated for 1 hour at 37° C under aerobic conditions. Glucose uptake and glycogen deposition were determined. Addition of adrenaline in vitro (1 μg/ml) caused a substantial decrease in glucose uptake in both types of diaphragms, this decrease being equivalent to a simultaneous inhibition of glycogen deposition. »Nembutal« anaesthesia prior to decapitation was found to alter the response to adrenaline. This change was most clearly observed in diaphragms of adrenalectomized rats. Here, adrenaline mainly affected glycogen metabolism by way of glycogen degradation, whereas the overall magnitude of the response was not materially changed. However, glucose uptake appeared to be only slightly decreased by adrenaline under these conditions. The change in response to adrenaline was attributed to the higher initial glycogen content observed in diaphragms of nembutalized rats. It was suggested that prevention of an acute release of endogenous adrenergic substances, occurring after decapitation of unanaesthetized donor rats, may be the actual cause of this phenomenon. Attention was drawn to the significance of the initial glycogen content as an important factor in carbohydrate metabolism of the isolated rat diaphragm.

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Distribution of newly formed hepatic glycogen in adrenalectomized rats as observed by radioautography after injection of 3H-galactose

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100111252 ◽

1984 ◽

Vol 42 ◽

pp. 228-229

Author(s):

J. E. Michaels ◽

J. T. Hung ◽

E. L. Cardell ◽

R. R. Cardell

Keyword(s):

Glycogen Synthesis ◽

Hepatic Glycogen ◽

Electron Microscopic ◽

Routine Procedures ◽

Silver Grains ◽

Synthetic Glucocorticoid ◽

Adrenalectomized Rats

In order to study early events of glycogen synthesis, we have used adrenalectomized (ADX) rats fasted overnight and injected with the synthetic glucocorticoid dexamethasone (DEX) to stimulate glycogen synthesis. Rats were given DEX 0-5 hr prior to sacrifice and injected with 2 mCi 3H-galactose 1 hr prior to sacrifice. Liver was prepared for light (LM) and electron microscopic (EM) radioautography by routine procedures.The concentration of silver grains over hepatic cytoplasm was measured in LM radioautographs using a Zeiss Videoplan. The hepatocytes were categorized as unlabeled if no silver grains (gr) were present, lightly labeled (<10gr/100 μm2 cytoplasm) or intensely labeled (>10 gr/1002 μm cytoplasm). Although very few hepatocytes showed heavy labeling after 1 hr treatment with DEX, by 2 hr after DEX treatment 8% of the cells distributed throughout the lobule were intensely labeled.

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Two isoprenylated flavonoids from Dorstenia psilurus activate AMPK, stimulate glucose uptake, inhibit glucose production and lower glycemia

Biochemical Journal ◽

10.1042/bcj20190326 ◽

2019 ◽

Vol 476 (24) ◽

pp. 3687-3704 ◽

Cited By ~ 2

Author(s):

Aphrodite T. Choumessi ◽

Manuel Johanns ◽

Claire Beaufay ◽

Marie-France Herent ◽

Vincent Stroobant ◽

...

Keyword(s):

Glucose Uptake ◽

Human Cancer ◽

Glucose Production ◽

Liver Mitochondria ◽

New Drugs ◽

Structural Isomer ◽

Rat Liver Mitochondria ◽

Ionization Mass ◽

Ampk Activation ◽

Starting Point

Root extracts of a Cameroon medicinal plant, Dorstenia psilurus, were purified by screening for AMP-activated protein kinase (AMPK) activation in incubated mouse embryo fibroblasts (MEFs). Two isoprenylated flavones that activated AMPK were isolated. Compound 1 was identified as artelasticin by high-resolution electrospray ionization mass spectrometry and 2D-NMR while its structural isomer, compound 2, was isolated for the first time and differed only by the position of one double bond on one isoprenyl substituent. Treatment of MEFs with purified compound 1 or compound 2 led to rapid and robust AMPK activation at low micromolar concentrations and increased the intracellular AMP:ATP ratio. In oxygen consumption experiments on isolated rat liver mitochondria, compound 1 and compound 2 inhibited complex II of the electron transport chain and in freeze–thawed mitochondria succinate dehydrogenase was inhibited. In incubated rat skeletal muscles, both compounds activated AMPK and stimulated glucose uptake. Moreover, these effects were lost in muscles pre-incubated with AMPK inhibitor SBI-0206965, suggesting AMPK dependency. Incubation of mouse hepatocytes with compound 1 or compound 2 led to AMPK activation, but glucose production was decreased in hepatocytes from both wild-type and AMPKβ1−/− mice, suggesting that this effect was not AMPK-dependent. However, when administered intraperitoneally to high-fat diet-induced insulin-resistant mice, compound 1 and compound 2 had blood glucose-lowering effects. In addition, compound 1 and compound 2 reduced the viability of several human cancer cells in culture. The flavonoids we have identified could be a starting point for the development of new drugs to treat type 2 diabetes.

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