Brzin M, Dettbarn W D, Rosenberg P, Nachmansohn D
J Cell Biol. 1965 Aug;26(2):353-64. doi: 10.1083/jcb.26.2.353.
According to theory, the action of acetylcholine (ACh) and ACh-esterase is essential for the permeability changes of excitable membranes during activity. It is, therefore, pertinent to know the activity of ACh-esterase per unit axonal surface area instead of per gram nerve, as it has been measured in the past. Such information has now been obtained with the newly developed microgasometric technique using a magnetic diver. (1) The cholinesterase (Ch-esterase) activity per mm(2) surface of sensory axons of the walking leg of lobster is 1.2 x 10(-3) microM/hr. (sigma = +/- 0.3 x 10(-3); SE = 0.17 x 10(-3)); the corresponding value for the motor axons isslightly higher: 1.93 x 10(-3) microM/hr. (sigma = +/- 0.41 x 10(-3); SE = +/- 0.14 x 10(-3)). Referred to gram nerve, the Ch-esterase activity of the sensory axons is much higher than that of the motor axons: 741 microM/hr. (sigma = +/- 73.5; SE = +/- 32.6) versus 111.6 microM/hr. (sigma = +/- 28.3; SE = +/- 10). (2) The enzyme activity in the small fibers of the stellar nerve of squid is 3.2 x 10(-4) microM/mm(2)/hr. (sigma = +/- 0.96 x 10(-4); SE = +/- 0.4 x 10(-4)). (3) The Ch-esterase activity per mm(2) surface of squid giant axon is 9.5 x 10(-5) microM/hr. (sigma = +/- 1.55 x 10(-5); SE = +/- 0.38 x 10(-5)). The value was obtained with small pieces of carefully cleaned axons after removal of the axoplasm and exposure to sonic disintegration. Without the latter treatment the figurewas 3.85 x 10(-5) microM/mm(2)/hr. (sigma = +/- 3.24 x 10(-5); SE = +/- 0.93 x 10(-5)). The experiments indicate the existence of permeability barriers in the cell wall surrounding part of the enzyme, since the substrate cannot reach all the enzyme even when small fragments of the cell wall are used without disintegration. (4) On the basis of the data obtained, some tentative approximations are made of the ratio of ACh released to Na ions entering the squid giant axon per cm(2) per impulse.
根据理论，乙酰胆碱（ACh）和乙酰胆碱酯酶的作用对于活动期间可兴奋膜的通透性变化至关重要。因此，了解每单位轴突表面积而非过去所测量的每克神经的乙酰胆碱酯酶活性是有意义的。现在已通过使用磁式潜水器的新开发的微量气体测量技术获得了此类信息。（1）龙虾步行腿感觉轴突每平方毫米表面的胆碱酯酶（Ch - 酯酶）活性为1.2×10⁻³微摩尔/小时。（标准差σ = ±0.3×10⁻³；标准误SE = 0.17×10⁻³）；运动轴突的相应值略高：1.93×10⁻³微摩尔/小时。（标准差σ = ±0.41×10⁻³；标准误SE = ±0.14×10⁻³）。以每克神经计，感觉轴突的Ch - 酯酶活性远高于运动轴突：741微摩尔/小时。（标准差σ = ±73.5；标准误SE = ±32.6），而运动轴突为111.6微摩尔/小时。（标准差σ = ±28.3；标准误SE = ±10）。（2）鱿鱼星状神经小纤维中的酶活性为3.2×10⁻⁴微摩尔/平方毫米/小时。（标准差σ = ±0.96×10⁻⁴；标准误SE = ±0.4×10⁻⁴）。（3）鱿鱼巨大轴突每平方毫米表面的Ch - 酯酶活性为9.5×10⁻⁵微摩尔/小时。（标准差σ = ±1.55×10⁻⁵；标准误SE = ±0.38×10⁻⁵）。该值是在去除轴浆并进行超声破碎后，用小心清洁的轴突小块获得的。未经后一种处理，该数值为3.85×10⁻⁵微摩尔/平方毫米/小时。（标准差σ = ±3.24×10⁻⁵；标准误SE = ±0.93×10⁻⁵）。实验表明，在围绕部分酶的细胞壁中存在通透性屏障，因为即使使用未破碎的细胞壁小片段，底物也无法接触到所有的酶。（4）根据所获得的数据，对每平方厘米每冲动释放的ACh与进入鱿鱼巨大轴突的钠离子的比例进行了一些初步估算。
