Liu B, Belke D D, Wang L C
Department of Pharmacology, University of Alberta, Edmonton, Canada.
Am J Physiol. 1997 Apr;272(4 Pt 2):R1121-7. doi: 10.1152/ajpregu.1997.272.4.R1121.
The Ca2+ uptake by isolated cardiac sarcoplasmic reticulum (SR) was compared between Richardson's ground squirrels and rats at 37, 25, 15, and 5 degrees C. The rate of SR Ca2+ uptake in ground squirrels was significantly higher than in rats over the temperature range. This marked species difference was observed over a Ca2+ concentration range from 0.1 to 10 microM. The Arrhenius plot for Ca2+ uptake was linear for ground squirrels between 37 and 5 degrees C but showed a depression from linearity for rats at 5 degrees C. This temperature sensitivity was also reflected in rat SR Ca2+-adenosinetriphosphatase activity. Analysis of [3H]ryanodine binding in SR suggests that more Ca2+ release channels are in an open state at low temperatures in rats than in ground squirrels. Together, these results suggest that species differences in the response of SR to low temperature may account for the rise in cytosolic free Ca2+ in cold-sensitive species and may be responsible, at least in part, for the inability of cold-sensitive hearts to function at low temperature.
在37、25、15和5摄氏度下，比较了理查森地松鼠和大鼠的离体心肌肌浆网（SR）对Ca2+的摄取情况。在地松鼠中，SR摄取Ca2+的速率在整个温度范围内均显著高于大鼠。在0.1至10微摩尔的Ca2+浓度范围内均观察到了这种显著的物种差异。地松鼠在37至5摄氏度之间，Ca2+摄取的阿伦尼乌斯曲线呈线性，但大鼠在5摄氏度时则偏离线性。这种温度敏感性也反映在大鼠SR的Ca2+-腺苷三磷酸酶活性上。对SR中[3H]ryanodine结合的分析表明，在低温下，大鼠SR中处于开放状态的Ca2+释放通道比地松鼠的更多。这些结果共同表明，SR对低温反应的物种差异可能是冷敏物种胞质游离Ca2+升高的原因，并且可能至少部分导致了冷敏心脏在低温下无法正常运作。
