Fiser B, Janík P
Physiol Bohemoslov. 1985;34(1):77-84.
Random stimulation of the perfused heart allows relationships between the rate of contractions (dP/dtmax), the size of contraction (Pmax) and the rate of relaxation (dP/dtmin) of contractions of varying intensity to be studied. The present study concerns these relationships during perfusion with ouabain, a low sodium medium and noradrenaline. Isolated rabbit hearts were perfused with Tyrode solution (O2 95%, CO2 5%, 36.4 degrees C), the isovolumic contractions of the left ventricle were recorded and the right ventricle was stimulated at random for 30 s (pulse width 10 ms, voltage double the threshold value). Perfusion was then switched over to perfusion with ouabain solution (10(-6) mol.l-1), with noradrenaline solution (10(-6) mol.l-1) or with low sodium solution (with 31% of the normal Na concentration). When spontaneous contraction size had attained a stable level, random stimulation was repeated. During random stimulation, dP/dtmin was directly proportional to Pmax (dP/dtmin = k1.P max) and to dP/dtmax (dP/dtmin = k2.dP/dtmax). Ouabain and low sodium did not change k1 or k2 and noradrenaline did not change k2. The increase in k1 during noradrenaline perfusion corresponds to shorter duration of contraction. It was found that dP/dtmax, which corresponds to the sarcoplasmic calcium concentration at the outset of activation, was the main factor determining the relaxation rate during ouabain, noradrenaline and low sodium perfusion.
对灌注心脏进行随机刺激，可研究不同强度收缩的收缩速率（dP/dtmax）、收缩幅度（Pmax）和舒张速率（dP/dtmin）之间的关系。本研究关注在哇巴因、低钠培养基和去甲肾上腺素灌注过程中的这些关系。将离体兔心脏用台氏液（O2 95%，CO2 5%，36.4℃）灌注，记录左心室的等容收缩，随机刺激右心室30秒（脉冲宽度10毫秒，电压为阈值的两倍）。然后将灌注切换为用哇巴因溶液（10^(-6) mol·l^(-1)）、去甲肾上腺素溶液（10^(-6) mol·l^(-1)）或低钠溶液（正常钠浓度的31%）进行灌注。当自发收缩幅度达到稳定水平时，重复随机刺激。在随机刺激期间，dP/dtmin与Pmax成正比（dP/dtmin = k1·Pmax），与dP/dtmax成正比（dP/dtmin = k2·dP/dtmax）。哇巴因和低钠不会改变k1或k2，而去甲肾上腺素不会改变k2。去甲肾上腺素灌注期间k1的增加对应于收缩持续时间的缩短。研究发现，对应于激活开始时肌浆钙浓度的dP/dtmax是决定哇巴因、去甲肾上腺素和低钠灌注期间舒张速率的主要因素。
