title: Effects of temperature and pH on cardiac myofilament Ca2+ sensitivity in rat and ground squirrel.
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.
authors.affiliation: Department of Zoology, University of Alberta, Edmonton, Canada.
authors.forename: B
authors.initials: B
authors.lastname: Liu
authors.forename: L C
authors.initials: LC
authors.lastname: Wang
authors.forename: D D
authors.initials: DD
authors.lastname: Belke
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006605:Hibernation / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D009200:Myocardial Contraction / Q000502:physiology; D010210:Papillary Muscles / Q000378:metabolism*; D010313:Partial Pressure; D051381:Rats; D017207:Rats, Sprague-Dawley; D012589:Sciuridae; D013696:Temperature
chemical_list: D002118:Calcium