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Investigative Ophthalmology & Visual Science, Vol 28, 850-858, Copyright © 1987 by Association for Research in Vision and Ophthalmology

ARTICLES AND REPORTS

Acetylcholinesterase activity in the cornea of the developing chick embryo

SA Sturges and GW Conrad

Activity of acetylcholinesterase (EC 3.1.1.7) and pseudocholinesterase (EC 3.1.1.8) was measured in extracts from chick corneas, in a developmental series from days 7-20 of incubation and at three ages after hatching. Enzyme activity was measured by the biphasic single- vial radiometric assay of Johnson and Russell using [3H-acetyl]choline as substrate. Pseudocholinesterase was inhibited with tetraisopropylpyrophosphoramide (iso-OMPA). True acetylcholinesterase activity was verified by control assays run in the presence of both iso- OMPA and the true acetylcholinesterase inhibitor, 1:5-bis(4- allyldimethyl-ammonium phenyl)-pentane-3-one diiodide (BW284c51). With both inhibitors present, no cholinesterase activity was detected. Corneal acetylcholinesterase had an average Km of 1.1 +/- 0.3 X 10(-3) M at day 7, 14, and 20 of development and retained 90% activity even after 3 hr at 26 degrees C. At least 90% of the total cholinesterase activity was solubilized by Triton X-100 and sonication treatment. Activity decreased with increasing concentrations of NaCl present in the assay. A 60-fold transient increase in acetylcholinesterase specific activity occurs during the period from days 7-20 of embryonic development. This increase begins on the first day measured (day 7), progresses steadily and rapidly during the subsequent week, reaches a peak at day 15, and then decreases rapidly before hatching to a level maintained into adulthood. A similar pattern of transient appearance of highly sialylated gangliosides seen previously on days 14-17 leads to an hypothesis of a structural linkage between acetylcholinesterase and the plasma membrane lipids of corneal epithelial cells.


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A. H. Conrad, Y. Zhang, A. R. Walker, L. A. Olberding, A. Hanzlick, A. J. Zimmer, R. Morffi, and G. W. Conrad
Thyroxine Affects Expression of KSPG-Related Genes, the Carbonic Anhydrase II Gene, and KS Sulfation in the Embryonic Chicken Cornea
Invest. Ophthalmol. Vis. Sci., January 1, 2006; 47(1): 120 - 132.
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Copyright © 1987 by the Association for Research in Vision and Ophthalmology