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Seasonal changes in supercooling points of blood plasma from the arctic ground squirrel evidence of masking of ice nucleators


FASEB Journal 18(4-5): Abst 238 19
Seasonal changes in supercooling points of blood plasma from the arctic ground squirrel evidence of masking of ice nucleators
The arctic ground squirrel (Spermophilus parryii) is the only mammal known to supercool and does so during hibernation by lowering core body temperature to—2.9degreesC (2.2degreesC below its equilibrium freezing point) without freezing or evidence of antifreeze activity. Towards understanding the mechanisms that allow S. parryii to supercool, we studied the seasonal variation in the freezing resistance of blood comparing samples taken from hibernating, field-active, and fed and fasted active animals. Fluid droplets (10mul) were cooled on an aluminum surface until they froze. Supercooling points (SCP) of whole blood, plasma, and serum from active animals did not differ. Plasma sampled from hibernating ground squirrels had SCP 5-6degreesC lower than plasma from active animals sampled in the summer, suggesting that animals either remove nucleators or add masking agents to neutralize nucleators prior to hibernation. A 24 hour fast had no effect on SCP of S. parryii plasma, however mixing serum from hibernating and active animals resulted in mean SCP that fell in-between values from hibernating and active animals. This is evidence of the potential presence of masking agents in serum of hibernating S. parryii. We conclude that the arctic ground squirrel exhibits seasonal changes in the supercooling point of its plasma and that this difference is likely caused by the introduction of masking agents prior to hibernating.

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Accession: 035701001



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