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 mm2 surface of sensory axons of the walking leg of lobster is 1.2 x 10-3 µM/hr. (σ = ± 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 µM/hr. (σ = ± 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 µM/hr. (σ = ± 73.5; SE = ± 32.6) versus 111.6 µM/hr. (σ = ± 28.3; SE = ± 10). (2) The enzyme activity in the small fibers of the stellar nerve of squid is 3.2 x 10-4 µM/mm2/hr. (σ = ± 0.96 x 10-4; SE = ± 0.4 x 10-4). (3) The Ch-esterase activity per mm2 surface of squid giant axon is 9.5 x 10-5 µM/hr. (σ = ± 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 µM/mm2/hr. (σ = ± 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 cm2 per impulse.
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1 August 1965
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August 01 1965
CHOLINESTERASE ACTIVITY PER UNIT SURFACE AREA OF CONDUCTING MEMBRANES
Miro Brzin,
Miro Brzin
From the Departments of Neurology and Biochemistry, College of Physicians and Surgeons, Columbia University, New York
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Wolf-Dietrich Dettbarn,
Wolf-Dietrich Dettbarn
From the Departments of Neurology and Biochemistry, College of Physicians and Surgeons, Columbia University, New York
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Philip Rosenberg,
Philip Rosenberg
From the Departments of Neurology and Biochemistry, College of Physicians and Surgeons, Columbia University, New York
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David Nachmansohn
David Nachmansohn
From the Departments of Neurology and Biochemistry, College of Physicians and Surgeons, Columbia University, New York
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Miro Brzin
From the Departments of Neurology and Biochemistry, College of Physicians and Surgeons, Columbia University, New York
Wolf-Dietrich Dettbarn
From the Departments of Neurology and Biochemistry, College of Physicians and Surgeons, Columbia University, New York
Philip Rosenberg
From the Departments of Neurology and Biochemistry, College of Physicians and Surgeons, Columbia University, New York
David Nachmansohn
From the Departments of Neurology and Biochemistry, College of Physicians and Surgeons, Columbia University, New York
Dr. Brzin's permanent address is Institute of Pathophysiology, University of Ljubljana, Yugoslavia
Received:
November 18 1964
Online ISSN: 1540-8140
Print ISSN: 0021-9525
Copyright © 1965 by The Rockefeller University Press
1965
J Cell Biol (1965) 26 (2): 353–364.
Article history
Received:
November 18 1964
Citation
Miro Brzin, Wolf-Dietrich Dettbarn, Philip Rosenberg, David Nachmansohn; CHOLINESTERASE ACTIVITY PER UNIT SURFACE AREA OF CONDUCTING MEMBRANES . J Cell Biol 1 August 1965; 26 (2): 353–364. doi: https://doi.org/10.1083/jcb.26.2.353
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