Effects of hibernation on fibrinolysis and platelet clot stability in 13‐lined ground squirrels

Abstract

During hibernation, a ground squirrel (Spermophilus tridecemlineatus) has decreased blood flow, which could lead to the formation of stasis blood clots. Ground squirrels have been shown to suppress blood clotting in order to survive hibernation. However, the stability of blood clots and the degradation process through fibrinolysis have not been determined. Preliminary results indicate no significant difference in plasminogen levels during hibernation. To see if fibrinolytic pathways were being activated during hibernation, plasmin activity was measured, and found to be 4‐fold higher in pooled hibernating versus pooled non‐hibernating plasma. These results suggest that fibrinolysis may be activated during hibernation, suggesting that some clots are still forming in spite of the suppression of hemostasis by the ground squirrels. A clot retraction assay was used to compare the stability of clots, and human platelet clots retracted in 45 minutes on average, compared with 25 minutes for non‐hibernating ground squirrels. The stability of blood clots in hibernating and non‐hibernating squirrels will be compared with the clot retraction assay when hibernating ground squirrel blood becomes available in the winter. A decreased stability of platelet clots may also protect ground squirrels from the formation of clots during hibernation. This research was funded by an NIH R15 grant.