Liver glycogen synthase and phosphorylase changes in vivo with hypoxia and anesthetics

Theen, J. W.; Gilboe, Daniel P.; Nuttall, F. Q.

doi:10.1152/ajpendo.1982.243.3.e182

Cited by 13 publications

(12 citation statements)

References 23 publications

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“…The anesthetic used has been shown not to result in activation of glycogen phosphorylase. An increase in the active form of phosphorylase has previously been shown to be an exquisitely sensitive indicator of hypoxemia and/or stress (14). We also have shown that the method used to procure liver samples, which were obtained while respiration and circulation were still intact, does not result in phosphorylase activation (14).…”

Section: Discussionmentioning

confidence: 72%

“…An increase in the active form of phosphorylase has previously been shown to be an exquisitely sensitive indicator of hypoxemia and/or stress (14). We also have shown that the method used to procure liver samples, which were obtained while respiration and circulation were still intact, does not result in phosphorylase activation (14). Two different methods of deproteinization were compared to ensure that deproteinization with an acid (HCIO 4 ) did not result in glycogenolysis.…”

Section: Discussionmentioning

confidence: 99%

“…Although blood samples usually were obtained from the portal vein, then from the aorta, and finally from the hepatic vein, the results were unchanged when blood samples were drawn in random order. While respiration and circulation were still intact, samples from the left lobe of the liver were freeze-clamped in situ with a clamp developed in our laboratory for this purpose (14). Samples were stored in liquid nitrogen until analyzed later the same day.…”

Section: Methodsmentioning

confidence: 99%

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Relationship of Hepatic Glucose Uptake to Intrahepatic Glucose Concentration in Fasted Rats After Glucose Load

Niewoehner

Nuttall²

1988

Diabetes

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Glucose concentration gradients across the liver and hepatic blood flow were measured to characterize the relationship of hepatic glucose uptake to hepatic glucose concentration for 240 min after administration of a large oral glucose load to fasted rats. Extraction of glucose occurred only transiently, from 20 to 80 min after glucose administration. The liver changed from net glucose output to net glucose removal only when the intracellular hepatic glucose concentration exceeded 12.5 mumol/ml water. Even when arteriovenous glucose concentrations gradients were compatible with net direct hepatic uptake of glucose, the hepatic glucose concentration always exceeded the inflow glucose concentration. These data indicate that direct glucose uptake occurred against a concentration gradient when the liver is considered as a whole. The hepatic intracellular-to-extracellular glucose concentration gradient changed very little, suggesting that this is not being regulated by glucose, insulin, or other effectors. The mechanism by which the hepatic glucose concentration and net hepatic glucose uptake versus output are coordinated is unknown. The rate of glycogen synthesis was linear for 120 min after administration of the glucose load. This occurred in the presence of direct uptake of glucose early in the time course and later in the presence of net glucose output by the liver. Net direct uptake of glucose by the liver could account for, at most, 37-55% of the glycogen formed. Fractional extraction of both lactate and alanine decreased after glucose was given, but net hepatic uptake of these metabolites could account for 33-49 and 7-10%, respectively, of the glycogen formed, depending on plasma versus blood water flow.(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Discussionmentioning

confidence: 72%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Relationship of Hepatic Glucose Uptake to Intrahepatic Glucose Concentration in Fasted Rats After Glucose Load

Niewoehner

Nuttall²

1988

Diabetes

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“…1 Phosphorylase a was increased in some, but not all, diabetic rats at 10-20 min after fructose gavage; this may have been due to stress from the gavage procedure (Table 2), because the phosphorylase a level has been shown to be exquisitely sensitive to stress. 20 In none of the animals was phosphorylase a decreased. By 60 min after fructose administration, phosphorylase a was unchanged from the control value.…”

Section: Diabetic Rats Normal Ratsmentioning

confidence: 94%

“…Within 10 s after the abdomen was opened, a section of liver was freeze-clamped in situ with a clamp developed in our laboratory for this purpose. 20 Liver samples were stored in liquid N 2 until analyzed later the same day. Animals were killed by removing the heart.…”

Section: Methodsmentioning

confidence: 99%

Mechanism of Stimulation of Liver Glycogen Synthesis by Fructose in Alloxan Diabetic Rats

Niewoehner

Nuttall

1986

Diabetes

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In diabetic animals and humans, stimulation of liver glycogen synthesis has been reported after administration of a large parenteral fructose load. The effects of an oral fructose load have not been examined previously. In the diabetic state, glycogen synthase phosphatase activity is reduced, and synthase D (the inactive form) is a poor substrate for the phosphatase. Thus, activation of synthase to the synthase R and synthase I (R + I) (active) forms by fructose would not be expected. We have determined that oral fructose administration does stimulate glycogen synthesis and have examined the mechanism by which this is accomplished. In 24-h-fasted alloxan diabetic rats, basal liver glycogen was higher than in normal rats (8.3 +/- 1.8 vs. 3.0 +/- 0.5 mg/g wet wt). After fructose (4 g/kg) was given, the initial rate of glycogen synthesis was normal in diabetic rats, but total glycogen synthesis was reduced. By 240 min, liver glycogen increased to 18 +/- 4.0 mg/g wet wt in diabetic rats versus 30.5 +/- 1.5 mg/g wet wt in normal rats. Synthase R + I was low and did not increase significantly (0.063 +/- 0.006 to 0.064 +/- 0.010 U/g wet wt) after fructose administration to the diabetic animals. Phosphorylase a did not decrease significantly during the period of active glycogen synthesis. In the diabetic rats, glucose-6-phosphate increased by 84% (0.103 +/- 0.010 to 0.184 +/- 0.020 mumol/g wet wt) within 10 min and remained elevated above the control level. UDPglucose decreased from 0.336 +/- 0.013 to 0.271 +/- 0.011 mumol/g wet wt at 10 min and remained below the control level.(ABSTRACT TRUNCATED AT 250 WORDS)

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Decreased hepatic glycogen content and accelerated response to starvation in rats with carbon tetrachloride-induced cirrhosis

1991

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Glucose homeostasis and fatty acid metabolism are abnormal in patients with cirrhosis. To assess the metabolic response to starvation in an animal model of cirrhosis, glycogen and fuel metabolism were characterized in rats with CCl4-induced cirrhosis studied 2 wk after 10 weekly doses of CCl4. Plasma concentrations of glucose and beta-hydroxybutyrate were not different between fed CCl4-treated and control rats, but plasma nonesterified fatty acid concentrations were higher in cirrhotic animals (0.25 +/- 0.01 vs. 0.39 +/- 0.04 mmol/L; p less than 0.05). After 12 hr of starvation, the plasma nonesterified fatty acid concentration had reached 0.58 +/- 0.04 mmol/L in CCl4-treated rats, compared with 0.38 +/- 0.04 mmol/L in control rats (p less than 0.05). The redistribution of the hepatic carnitine pool toward acylcarnitines, which is characteristic of starvation, was complete after fasting for 12 hr in the CCl4-treated rats, compared with the 24 hr required in control rats. In fed cirrhotic rats, liver glycogen content per gram liver was decreased by 64% compared with control rats (30.0 +/- 5.1 vs. 10.8 +/- 1.1 mg/gm liver wet wt; p less than 0.05). After 12-hr fasting, hepatic glycogen content had fallen to 14.3 +/- 3.9 and 4.8 +/- 0.4 mg/gm liver wet wt (p less than 0.05) in control and cirrhotic animals, respectively. To further characterize the status of glycogen metabolism in cirrhotic livers, activities of glycogen synthase and glycogen phosphorylase were determined. Hepatic active and total glycogen phosphorylase activities normalized to hepatocellular content were unaffected by CCl4 treatment, whereas total glycogen synthase activity was increased by 45%.(ABSTRACT TRUNCATED AT 250 WORDS)

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Liver glycogen synthase and phosphorylase changes in vivo with hypoxia and anesthetics

Cited by 13 publications

References 23 publications

Relationship of Hepatic Glucose Uptake to Intrahepatic Glucose Concentration in Fasted Rats After Glucose Load

Relationship of Hepatic Glucose Uptake to Intrahepatic Glucose Concentration in Fasted Rats After Glucose Load

Mechanism of Stimulation of Liver Glycogen Synthesis by Fructose in Alloxan Diabetic Rats

Decreased hepatic glycogen content and accelerated response to starvation in rats with carbon tetrachloride-induced cirrhosis

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