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  • Title: Effects of temperature and pH on cardiac myofilament Ca2+ sensitivity in rat and ground squirrel.
    Author: Liu B, Wang LC, Belke DD.
    Journal: Am J Physiol; 1993 Jan; 264(1 Pt 2):R104-8. PubMed ID: 8430869.
    Abstract:
    Chemically skinned papillary muscles from active and hibernating ground squirrels were used to determine whether the enhanced cardiac contractility observed in hibernation is due to a change in myofilament Ca2+ sensitivity. A similar preparation from rats was used to reflect the changes in a nonhibernator. When examined at pH 7.00 in all three groups and under physiological pH with varying temperatures in the ground squirrels, the calcium concentration at which muscle tension is at 50% maximum (pCa2+50) decreased significantly (P < 0.05) with decreasing temperature (25, 15, and 5 degrees C). When hibernating and active ground squirrels were compared, no significant difference in pCa2+50 was observed at 25 degrees C; however, the values at 15 and 5 degrees C were significantly higher (P < 0.05) in the hibernating squirrels. The results indicate that cardiac myofilament Ca2+ sensitivity decreases significantly at low temperature in both active and hibernating ground squirrels; however, the higher Ca2+ sensitivity in the hibernating squirrels at 15 and 5 degrees C could partially contribute to the enhanced cardiac contractility typically seen during hibernation.
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