Facilitation by ‘low sodium-urea’ medium of the washout of dopamine β-hydroxylase released by potassium ions from the perfused rabbit heart
Facilitation by ‘low sodium-urea’ medium of the washout of dopamine β-hydroxylase released by potassium ions from the perfused rabbit heart
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“低钠尿素”介质促进灌注兔心脏钾离子释放的多巴胺β-羟化酶的冲洗
DOI：
10.1016/0306-4522(80)90120-7
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发表时间：
1980
期刊：
影响因子：
3.3
通讯作者：
H. Ritzel
中科院分区：
文献类型：
--
作者：
E. Muscholl;K. Racké;H. Ritzel
用高K-低Na溶液（用KCl等摩尔取代台氏溶液的132 mM NaCl）以恒定流速灌注兔心脏2或30 min。高钾低钠溶液灌流30 min可引起去甲肾上腺素的大量分泌，在0-5 min达高峰，随后随时间呈指数下降。而多巴胺β-羟化酶则缓慢上升，在15-20 min达最大值，即使给予高钾低钠溶液2 min，多巴胺β-羟化酶也不能产生峰值。去甲肾上腺素和多巴胺β-羟化酶输出缺乏一致性可能是由于酶的缓慢洗脱或多巴胺β-羟化酶与去甲肾上腺素在15分钟时的比例大于5分钟时的比例。乙酰甲胆碱（320 μM）或钙剥夺优先阻断初始去甲肾上腺素溢出，大大减少了多巴胺β-羟化酶的总输出，并消除了多巴胺β-羟化酶。在以下实验中，使用低Na-尿素溶液（用242 mM尿素替代台氏溶液的132 mM NaCl）来加速多巴胺β-羟化酶的洗脱。用高钾低钠溶液灌注心脏2 min，然后用低钠尿素溶液灌注，在5-10 min时已诱发多巴胺β-羟化酶峰值。多巴胺β-羟化酶的总输出量大于高钾低钠溶液和低钠尿素溶液的预期输出量之和。去甲肾上腺素的总输出量约为高钾低钠和低钠尿素灌流时的总和，提示高钾低钠介质引起的多巴胺β-羟化酶释放的最大速率与去甲肾上腺素的初始大量溢出同时发生，这种溢出是钙依赖性的，并受到突触前M抑制。然而，与小分子相比，大分子的洗脱有延迟。因此，低Na-尿素溶液可用作加速从灌注的兔心脏中洗脱多巴胺β-羟化酶的工具。
Rabbit hearts were perfused for 2 or 30 min at a constant flow with high K-low Na solution (equimolar substitution of 132 mM NaCl of Tyrode's solution by KCl). The perfusates were collected in 5 min periods and assayed for noradrenaline and dopamine β-hydroxylase activity.High K-low Na solution perfused for 30 min caused a pronounced noradrenaline output with the peak at 0–5 min which subsequently declined exponentially with time. In contrast, the dopamine β-hy-droxylase output rose slowly to its maximum at 15–20 min. If high K-low Na solution was administered for 2 min it failed to produce a peak in the output of dopamine β-hydroxylase. The lack of coincidence of noradrenaline and dopamine β-hydroxylase outputs might have been due to either a slow washout of the enzyme or to a larger ratio of dopamine β-hydroxylase to noradrenaline at 15 than at 5 min.Methacholine (320 μM) or calcium deprivation which preferentially blocked the initial noradrenaline overflow greatly reduced the total output of dopamine β-hydroxylase and abolished the dopamine β-hydroxylase peak at 15–20 min. In the following experiments low Na-urea solution (substitution of 132 mM NaCl of Tyrode's solution by 242 mM urea) was employed to accelerate the washout of dopamine β-hydroxylase. Perfusion of the hearts with high K-low Na for 2 min, followed by low Na-urea solution, evoked a dopamine β-hydroxylase peak already at 5–10 min. The total output of dopamine β-hydroxylase was larger than the combined outputs to be expected of high K-low Na and low Na-urea solutions. The total noradrenaline output was approximately the sum of that during high K-low Na and low Na-urea perfusion.It is concluded that the maximum rate of dopamine β-hydroxylase release evoked by high K-low Na medium occurs at the same time as the initial large noradrenaline overflow that is calcium-dependent and subject to presynaptic muscarinic inhibition. However, there is a delay in the washout of the large compared with the small molecule. Thus, low Na-urea solution can be used as a tool to accelerate the washout of dopamine β-hydroxylase from the perfused rabbit heart.