Chang K C, Schreur J H, Weiner M W, Camacho S A
Department of Medicine, University of California, San Francisco 94143, USA.
Am J Physiol. 1996 Jul;271(1 Pt 2):H228-34. doi: 10.1152/ajpheart.1996.271.1.H228.
Both cytosolic free Ca2+ ([Ca2+]i) decline and myocardial relaxation are slowed in severe hypertrophy and heart failure. However, it is not certain whether this occurs in mild to moderate hypertrophy. Therefore, we tested the hypotheses that slowing of [Ca2+]i decline 1) occurs in mild to moderate hypertrophy, 2) occurs in the absence of slowed relaxation, and 3) is related to the degree of hypertrophy. Experiments were performed on isolated rat hearts subjected to pressure overload. Indo 1 fluorescence was used as an index of [Ca2+]i. [Ca2+]i decline and myocardial relaxation were assessed by the time constant of exponential [Ca2+]i decline (tau Ca) and left ventricular (LV) pressure decline (tau p), respectively. Mean tau Ca was significantly increased in hearts from banded rats compared with sham-operated rats (59 +/- 13 vs. 45 +/- 5 ms, P = 0.03). In contrast, there was no difference in mean tau p (28 +/- 3 vs. 29 +/- 5 ms, P = not significant). There was a linear relationship between tau Ca and LV dry weight (r = 0.79). In summary, slowing of the [Ca2+]i transient decline occurred in mild to moderate hypertrophy. However, LV relaxation was unaffected. Furthermore, slowing of the [Ca2+]i transient decline was closely related to the degree of LV hypertrophy. These data suggest that slowing of [Ca2+]i decline is an early manifestation of pressure-overload hypertrophy that precedes slowing of relaxation.
在严重肥大和心力衰竭时，胞浆游离钙（[Ca2+]i）下降和心肌舒张均减慢。然而，在轻度至中度肥大时是否会出现这种情况尚不确定。因此，我们检验了以下假设：[Ca2+]i下降减慢1）发生在轻度至中度肥大中，2）在舒张未减慢的情况下发生，3）与肥大程度相关。对压力超负荷的离体大鼠心脏进行了实验。Indo 1荧光用作[Ca2+]i的指标。分别通过指数[Ca2+]i下降的时间常数（tau Ca）和左心室（LV）压力下降（tau p）评估[Ca2+]i下降和心肌舒张。与假手术大鼠相比，结扎大鼠心脏的平均tau Ca显著增加（59±13对45±5毫秒，P = 0.03）。相比之下，平均tau p无差异（28±3对29±5毫秒，P =不显著）。tau Ca与LV干重之间存在线性关系（r = 0.79）。总之，[Ca2+]i瞬时下降减慢发生在轻度至中度肥大中。然而，LV舒张未受影响。此外，[Ca2+]i瞬时下降减慢与LV肥大程度密切相关。这些数据表明，[Ca2+]i下降减慢是压力超负荷肥大的早期表现，早于舒张减慢。
