Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

Wood frogs (Rana sylvatica) utilize high extracellular glucose concentrations as a cryoprotectant during periods of subzero environmental temperatures when extracellular fluids are frozen. Initiation of a freezing event in these frogs is characterized by a brief period of high extracellular glucose concentration with no apparent increase in glucose utilization. The biochemical basis for this block in glucose utilization was investigated using erythrocytes. The data revealed a temperature-specific profound glycolytic blockage that was apparent only at 4oC. At this temperature, 13C-NMR spectra showed the accumulation of fructose and, possibly glucose 6-phosphate and fructose 6-phosphate suggesting that the temperature-sensitive enzyme is PFK. NMR data also revealed that only 5% of a 200 mM glucose incubation was converted into glycolytic intermediates after 34 h at 4oC confirming a blockage at the initial stages of glycolysis. Glucose transport into the erythrocyte was not affected by temperature. 31P-NMR analysis of Rana sylvatica erythrocytes showed that the temperature block was not the result of a lower pH (which could inhibit PFK): intracellular pH increased from 7.3 to 8.1 with decreasing assay temperature from 17oC to 4oC. The relative concentrations of ATP were independent of glucose loading levels and temperature changes indicating that ATP is not involved in the regulation of glycolysis by temperature.

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Poster Number PAbrooks0296
Keywords: Freeze tolerance, frogs, glycolysis, temperature, phosphofructokina