成年大鼠心脏中的胆碱乙酰转移酶
Choline acetyltransferase in the heart of adult rats.
作者信息
Slavíková J, Tucek S
出版信息
Pflugers Arch. 1982 Jan;392(3):225-9. doi: 10.1007/BF00584300.
The distribution of choline acetyltransferase (ChAT, EC 2.3.1.6.) in the heart of adult rats has been reinvestigated in view of recent discoveries that acetylcholine (ACh) can be synthesized not only by ChAT, but also by carnitine acetyltransferase (CarAT, EC 2.3.1.7) and that it is possible to distinquish between the ACh-synthesizing activity of ChAT in intramuscular nerves and the CarAT-mediated extraneural synthesis of ACh by means of bromoacetylcholine (BrACh), a specific inhibitor of ChAT. BrACh (0.002 mmol/l) has been found to inhibit the synthesis of ACh in the atria by 66-85% and in the ventricles by only 19-29%. Bromoacetylcarnitine (BrACar, 0.02 mmol/l), and inhibitor of CarAT, inhibited the synthesis of ACh in the atria by 34% and in the ventricles by 74-80%. These findings indicate that ChAT is responsible for most of the synthesis of ACh observed in the homogenates of the atria; in the ventricles, it catalyses only a minor portion of the total ACh synthesis observed. In the investigation of the regional distribution of ChAT in the heart, the BrACh-sensitive part of ACh synthesis was taken as the measure of ChAT activity. The highest activity of ChAT (nmol ACh synthesized g-l.h-l) was found in the region of the sinoatrial node (1775); it decreased in the order: interatrial septum (781) greater than rest of the right atrium (712) greater than left atrium (416) greater than basal part of the right ventricle (366) greater than apical part of the right ventricle (250) greater than inter-ventricular septum (239) greater than basal and apical part of the left ventricle (208 and 205). The results indicate that earlier investigations of the distribution of ChAT in the heart provided a basically correct picture although the contribution of CarAT to the synthesis of ACh measured had not been excluded, and confirm that ChAT is present throughout the heart, including the apical parts of the ventricles, However, the sino-atrio-ventricular gradient of ChAT distribution is steeper when the contribution of CarAT to the synthesis of ACh is excluded.
鉴于最近的发现，即乙酰胆碱（ACh）不仅可以由胆碱乙酰转移酶（ChAT，EC 2.3.1.6）合成，还可以由肉碱乙酰转移酶（CarAT，EC 2.3.1.7）合成，并且可以通过ChAT的特异性抑制剂溴乙酰胆碱（BrACh）区分肌内神经中ChAT的ACh合成活性和CarAT介导的神经外ACh合成，因此对成年大鼠心脏中胆碱乙酰转移酶（ChAT）的分布进行了重新研究。已发现BrACh（0.002 mmol/l）可使心房中ACh的合成抑制66 - 85%，而在心室中仅抑制19 - 29%。肉碱乙酰转移酶（CarAT）的抑制剂溴乙酰肉碱（BrACar，0.02 mmol/l）可使心房中ACh的合成抑制34%，在心室中抑制74 - 80%。这些发现表明，ChAT是心房匀浆中观察到的大部分ACh合成的原因；在心室中，它仅催化观察到的总ACh合成的一小部分。在研究心脏中ChAT的区域分布时，将ACh合成中对BrACh敏感的部分作为ChAT活性的指标。发现ChAT的最高活性（每克每小时合成的ACh纳摩尔数）出现在窦房结区域（1775）；其活性按以下顺序降低：房间隔（781）＞右心房其余部分（712）＞左心房（416）＞右心室基部（366）＞右心室尖部（250）＞室间隔（239）＞左心室基部和尖部（208和205）。结果表明，尽管未排除CarAT对所测ACh合成的贡献，但早期关于心脏中ChAT分布的研究提供了基本正确的情况，并证实ChAT存在于整个心脏，包括心室尖部。然而，当排除CarAT对ACh合成的贡献时，ChAT分布的窦房 - 心室梯度更陡。
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