[Experimental analysis of the calcium source for cardiac excitation-contraction coupling in hibernator Citellus dauricus].
The force-interval and force-frequency relationships and the effects of Cd2+ and ryanodine on the myocardial action potential and contraction were compared between hibernating (HGS) and active (AGS) ground squirrels Citellus dauricus. (1) Raising the driving frequency caused a negative inotropic effect in the AGS group, but a biphasic change with an increase of the peak force followed by a decrease in the HGS group. The contraction in HGS group exhibited a more pronounced post-interval potentiation, and was more significantly modulated by the driving frequency. (2) HGS animals displaged action potentials of shorter early-stage duration and stronger contractions of shorter time course in comparison with the AGS animals. Both the action potential and the contraction of HGS group were less affected by Cd2+, but the contraction was more significantly inhibited by ryanodine than that of the AGS group. Our results suggested that dependence of cardiac excitation-contraction coupling on calcium influx was weakened, while the function of sarcoplasmic reticulum as a source of activator Ca2+ was enhanced during hibernation, which might take an important part in the cold-tolerant adaptation of hibernating hearts.
Wang
S Q
SQ
College of Life Sciences, Peking University, Beijing.
Feng
Q
Q
Zhou
Z Q
ZQ
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001693:Biological Transport, Active; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D006605:Hibernation / Q000502:physiology*; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D012433:Ryanodine / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D012589:Sciuridae; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D014662:Vasoconstrictor Agents; D002104:Cadmium; D012433:Ryanodine; D002118:Calcium