ARTICLE

THE LOCALIZATION OF CHOLINESTERASE ACTIVITY IN RAT CARDIAC MUSCLE BY ELECTRON MICROSCOPY

¹ From the Department of Pathology, Harvard Medical School, Boston

A method has been developed for localizing sites of cholinesterase activity in rat cardiac muscle by electron microscopy. The method utilizes thiocholine esters as substrates, and is believed to be dependent on the reduction of ferricyanide to ferrocyanide by thiocholine released by enzymatic activity. The ferrocyanide thus formed is captured by copper to form fine, electron-opaque deposits of copper ferrocyanide, which sharply delineate sites of enzymatic activity at the ultrastructural level. Cholinesterase activity in formalin-fixed heart muscle was localized: (a) in longitudinal elements of the sarcoplasmic reticulum, but not in the T, or transverse, elements; and (b) in the A band, with virtually no activity noted in the M band, or in the H zone. The I band was also negative. No activity was detected in the sarcolemma, or in invaginations of the sarcolemma at the level of the Z band. The perinuclear element of the sarcoplasmic (endoplasmic) reticulum was frequently strongly positive. Activity at all sites was completely abolished by omitting the substrates, or by inhibition with eserine 10^-4 M and diisopropylfluorophosphate 10^-5 M. Eserine 10^-5 M completely inhibited reaction in the sarcoplasmic reticulum, and virtually abolished that in the A band. These observations, together with the use of the relatively specific substrates and suitable controls to eliminate non-enzymatic staining, indicate that cholinesterase activity was being demonstrated. The activity in rat heart against different substrates was that of non-specific cholinesterases, in accordance with biochemical data. The activity in the A band was considered to be probably due to myosincholinesterase. It is proposed that the localization of cholinesterases in myocardium at the ultrastructural level should be taken into account in considering the possible functions of these myocardial enzymes, and it is hoped that knowledge of their localization will open up new avenues of approach in considering their physiological role in myocardium, which at present is not definitely known.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Facebook    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

• Kang, H., Tian, L., Son, Y.-J., Zuo, Y., Procaccino, D., Love, F., Hayworth, C., Trachtenberg, J., Mikesh, M., Sutton, L., Ponomareva, O., Mignone, J., Enikolopov, G., Rimer, M., Thompson, W. (2007). Regulation of the Intermediate Filament Protein Nestin at Rodent Neuromuscular Junctions by Innervation and Activity. J. Neurosci. 27: 5948-5957 [Abstract] [Full Text]  
• Yang, J.-F., Cao, G., Koirala, S., Reddy, L. V., Ko, C.-P. (2001). Schwann Cells Express Active Agrin and Enhance Aggregation of Acetylcholine Receptors on Muscle Fibers. J. Neurosci. 21: 9572-9584 [Abstract] [Full Text]  
• Deconinck, A. E., Potter, A. C., Tinsley, J. M., Wood, S. J., Vater, R., Young, C., Metzinger, L., Vincent, A., Slater, C. R., Davies, K. E. (1997). Postsynaptic Abnormalities at the Neuromuscular Junctions of Utrophin-deficient Mice. JCB 136: 883-894 [Abstract] [Full Text]  
• Rotundo, R. L., Rossi, S. G., Anglister, L. (1997). Transplantation of Quail Collagen-tailed Acetylcholinesterase Molecules Onto the Frog Neuromuscular Synapse. JCB 136: 367-374 [Abstract] [Full Text]  
• Missias, A., Mudd, J, Cunningham, J., Steinbach, J., Merlie, J., Sanes, J. (1997). Deficient development and maintenance of postsynaptic specializations in mutant mice lacking an 'adult' acetylcholine receptor subunit. Development 124: 5075-5086 [Abstract]  
• Jo, S., Burden, S. (1992). Synaptic basal lamina contains a signal for synapse-specific transcription. Development 115: 673-680 [Abstract]  
• Nitkin, R.M., Wallace, B.G., Spira, M.E., Godfrey, E.W., McMahan, U.J. (1983). Molecular Components of the Synaptic Basal Lamina That Direct Differentiation of Regenerating Neuromuscular Junctions. Cold Spring Harb Symp Quant Biol 48: 653-665 [Abstract]  
• Sanes, J.R., Chiu, A.Y. (1983). The Basal Lamina of the Neuromuscular Junction. Cold Spring Harb Symp Quant Biol 48: 667-678 [Abstract]  
• Chokroverty, S., Reyes, M. G., Rubino, F. A., Barron, K. D. (1976). Hemiplegic Amyotrophy: Muscle and Motor Point Biopsy Study. Arch Neurol 33: 104-110 [Abstract]  
• Frank, E., Gautvik, K., Sommerschild, H. (1976). Persistence of Junctional Acetylcholine Receptors following Denervation. Cold Spring Harb Symp Quant Biol 40: 275-281 [Abstract]  
• Bjornskov, E. K., Dekker, N. P., Norris, F. H. Jr, Stuart, M. E. (1975). End-Plate Morphology in Amyotrophic Lateral Sclerosis. Arch Neurol 32: 711-712 [Abstract]  

Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents