Electrophoretic analysis of liver glycogen phosphorylase activation in the freeze-tolerant wood frog

1988 ◽  
Vol 971 (1) ◽  
pp. 72-84
Author(s):  
Michael M. Crerar ◽  
Emina S. David ◽  
Kenneth B. Storey
Keyword(s):  
Glycogen Phosphorylase ◽  
Liver Glycogen ◽  
Electrophoretic Analysis ◽  
Wood Frog ◽  
Freeze Tolerant

Glucose and caffeine regulation of liver glycogen phosphorylase activity in the freeze-tolerant wood frog Rana sylvatica

1991 ◽  
Vol 69 (4) ◽  
pp. 251-255 ◽  
Author(s):  
Carey A. Risman ◽  
Emina S. David ◽  
Kenneth B. Storey ◽  
Michael M. Crerar
Keyword(s):  
Dissociation Constant ◽  
Glycogen Phosphorylase ◽  
Rana Sylvatica ◽  
Liver Glycogen ◽  
Significant Inhibition ◽  
Phosphorylase Activity ◽  
Interaction Factor ◽  
Mammalian Enzyme ◽  
Freeze Tolerant

We have examined the effect of glucose and caffeine inhibition on the activity of liver glycogen phosphorylase a from the freeze-tolerant frog Rana sylvatica. Kinetic studies indicate that this enzyme exhibits similar sensitivity to glucose inhibition (glucose dissociation constant = 12.5 mM) as the mammalian enzyme. Little inhibition (< 25%) was observed at normal glucose concentrations (1–5 mM), while significant inhibition (60–95%) occurred at glucose concentrations (50–500 mM) present in freezing-exposed animals. These results favour the hypothesis that in the normal state glucose regulates phosphorylase activity primarily through the promotion of dephosphorylation of phosphorylase a, whereas during freezing regulation is achieved through phosphorylase a inactivation. The caffeine dissociation constant (0.93 mM) and the degree of synergism between caffeine and glucose (interaction factor, α = 0.14) were also similar to that observed for the mammalian enzyme. Hence, if a caffeine-like ligand exists in vivo, it must be in low enough amounts during freezing to allow sufficient phosphorylase a activity for high glucose production.Key words: glycogen phosphorylase, glucose regulation, caffeine inhibition, freeze tolerance, cryoprotection.

Cryoprotectant production capacity of the freeze-tolerant wood frog, Rana sylvatica

1993 ◽  
Vol 71 (1) ◽  
pp. 71-75 ◽  
Author(s):  
Jon P. Costanzo ◽  
Richard E. Lee Jr.
Keyword(s):  
Production Capacity ◽  
Rana Sylvatica ◽  
Freeze Tolerance ◽  
Liver Glycogen ◽  
Wood Frog ◽  
Freezing Injury ◽  
Wood Frogs ◽  
Cryoprotectant Synthesis ◽  
Freeze Tolerant ◽  
The Relationship

Freezing survival of the wood frog (Rana sylvatica) is enhanced by the synthesis of the cryoprotectant glucose, via liver glycogenolysis. Because the quantity of glucose mobilized during freezing bears significantly on the limit of freeze tolerance, we investigated the relationship between the quantity of liver glycogen and the capacity for cryoprotectant synthesis. We successfully augmented natural levels of liver glycogen by injecting cold-conditioned wood frogs with glucose. Groups of 8 frogs having mean liver glycogen concentrations of 554 ± 57 (SE), 940 ± 57, and 1264 ± 66 μmol/g catabolized 98.7, 83.4, and 52.8%, respectively, of their glycogen reserves during 24 h of freezing to −2.5 °C. Glucose concentrations concomitantly increased, reaching 21 ± 3, 102 ± 23, and 119 ± 14 μmol/g, respectively, in the liver, and 15 ± 3, 42 ± 5, and 61 ± 5 μmol/mL, respectively, in the blood. Because the capacity for cryoprotectant synthesis depends on the amount of liver glycogen, the greatest risk of freezing injury likely occurs during spring, when glycogen reserves are minimal. Non-glucose osmolites were important in the wood frog's cryoprotectant system, especially in frogs having low glycogen levels. Presumably the natural variation in cryoprotectant synthesis capacity among individuals and populations of R. sylvatica chiefly reflects differences in glycogen reserves; however, environmental, physiological, and genetic factors likely are also involved.

Temporal patterns of tissue glycogen, glucose, and glycogen phosphorylase activity prior to hibernation in freeze-tolerant chorus frogs, Pseudacris triseriata

2008 ◽  
Vol 86 (10) ◽  
pp. 1095-1100 ◽  
Author(s):  
Steve C. Dinsmore ◽  
David L. Swanson
Keyword(s):  
Glycogen Phosphorylase ◽  
Threshold Level ◽  
Liver Glycogen ◽  
Critical Threshold ◽  
Hepatic Glycogen ◽  
Phosphorylase Activity ◽  
Continuous Increase ◽  
Glycogen Accumulation ◽  
Chorus Frogs ◽  
Glycogen Stores

Freezing survival may differ among winters in chorus frogs ( Pseudacris triseriata (Wied-Neuwied, 1838)), and low freezing survival is associated with low hepatic glycogen stores. The pattern of prehibernation liver glycogen accumulation in chorus frogs is unknown. Frogs might accumulate hepatic glycogen stores until a threshold level sufficient for winter survival is attained, after which frogs enter hibernation (critical threshold hypothesis). According to this model, frogs active late in the season should only be those with low hepatic glycogen stores. Alternatively, hepatic glycogen levels might continue to increase throughout the fall as long as frogs remain active (continuous increase hypothesis). We tested these hypotheses by measuring liver and leg muscle glycogen, glucose, and glycogen phosphorylase activities in chorus frogs throughout the fall prehibernation period in southeastern South Dakota. Hepatic glycogen levels were significantly related to date and increased throughout the fall period, consistent with the continuous increase hypothesis. This suggests that hepatic glycogen levels do not serve as a cue for entrance into hibernation. Liver phosphorylase activity did not vary significantly with progression of the fall season and activity was lower than in winter, suggesting that the winter increment of phosphorylase activity requires some stimulus during hibernation (e.g., low temperatures).

scholarly journals Heterologous desensitization of the cyclic AMP-independent glycogenolytic response in rat liver cells

1981 ◽  
Vol 200 (3) ◽  
pp. 509-514 ◽  
Author(s):  
B Bréant ◽  
S Keppens ◽  
H De Wulf
Keyword(s):  
Cyclic Amp ◽  
Glycogen Phosphorylase ◽  
Liver Glycogen ◽  
Receptor Interaction ◽  
Alpha Adrenergic Receptors ◽  
Rat Liver Cells ◽  
Heterologous Desensitization ◽  
Highly Correlated ◽  
Alpha Agonist

Vasopressin and alpha-adrenergic agonists are known to be potent cyclic AMP-independent Ca2+-dependent activators of liver glycogen phosphorylase. When hepatocytes are pre-incubated with increasing concentrations of vasopressin or of the alpha-agonist phenylephrine, they become progressively unresponsive to a second addition of the respective agonist. The relative abilities of six vasopressin analogues and of five alpha-agonists to activate glycogen phosphorylase and to cause subsequent desensitization are highly correlated, indicating that the same vasopressin and alpha-adrenergic receptors are involved in both responses. About 5-times-higher peptide concentrations are needed to desensitize the cells than to activate their glycogen phosphorylase, whereas the concentrations of alpha-agonists required for the desensitization are only twice those needed for the activation of phosphorylase. The desensitization is not mediated by a perturbation in the agonist-receptor interaction. It is clearly heterologous, i.e. it is not agonist-specific, and must therefore involve a mechanism common to both series of agonists. The evidence for a role of Ca2+ movements or phosphatidylinositol turnover is briefly discussed.

Freeze-thaw injury in erythrocytes of the freeze-tolerant wood frog, Rana sylvatica

1991 ◽  
Vol 261 (6) ◽  
pp. R1346-R1350 ◽  
Author(s):  
J. P. Costanzo ◽  
R. E. Lee
Keyword(s):  
Cell Injury ◽  
Osmotic Fragility ◽  
Rana Sylvatica ◽  
Freeze Tolerance ◽  
Wood Frog ◽  
In Vitro Tests ◽  
Freezing And Thawing ◽  
Freeze Tolerant ◽  
High Concentrations

Erythrocytes from the freeze-tolerant wood frog (Rana sylvatica) were subjected to in vitro tests of freeze tolerance, cryoprotection, and osmotic fragility. The responses of cells from frogs acclimated to 4 or 15 degrees C were similar. Erythrocytes that were frozen in saline hemolyzed at -4 degrees C or lower. The addition of high concentrations (150 and 1,500 mM) of glucose or glycerol, cryoprotectants produced naturally by freeze-tolerant frogs, significantly reduced cell injury at -8 degrees C, but concentrations of 1.5 or 15 mM were ineffective. Hemolysis was reduced by 94% with 1,500 mM glycerol and by 84% with 1,500 mM glucose; thus glycerol was the more effective cryoprotectant. Mean fragility values for frog erythrocytes incubated in hypertonic and hypotonic saline were 1,938 and 49 mosM, respectively. Survival in freeze tolerance and cryoprotection experiments was comparable for erythrocytes from frogs and humans, suggesting that these cells may respond similarly to freezing-related stresses. However, the breadth of osmotic tolerance, standardized for differences in isotonicity, was greater for frog erythrocytes than for human erythrocytes. Our data suggest that erythrocytes from R. sylvatica are adequately protected by glucose under natural conditions of freezing and thawing.

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