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Human Retinas Synthesize and Release Acetylcholine
Author(s) -
Hutchins James B.,
Hollyfield Joe G.
Publication year - 1986
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1986.tb02834.x
Subject(s) - acetylcholine , choline , retina , chemistry , potassium , enzyme , retinal , chromatography , biochemistry , cholinergic , biology , endocrinology , organic chemistry , neuroscience
Human retinas have the capacity to synthesize and release [ 3 H]acetylcholine ([ 3 H]ACh) after an incubation in [ 3 H]choline ([ 3 H]Ch). Synthesis of [ 3 H]Ch by retinal homogenates was determined using either high‐voltage paper electrophoresis (HVPE) or a two‐step enzymatic/extraction assay for separating [ 3 H]ACh from pH]Ch. The enzymatic/extraction assay is shown to be accurate over a wide range of concentrations (10 ‐6 ‐10 ‐12 M ). Homogenates of human retina synthesize [ 3 H]ACh from [ 3 H]Ch. We find an approximate K m of 50 μ M and a V max of about 20 nmol/mg protein/h (at 37°C) for the synthesis of labeled ACh by retinal homogenates. Human retinas also release [ 3 H]ACh after a pulse of [ 3 H]Ch. Release of labeled transmitter is stimulated by potassium depolarization. The potassium‐stimulated release is partially blocked by magnesium or cobalt ions. Release data were analyzed by both the enzymatic/extraction assay and HVPE; the results are qualitatively identical in both cases. The data reported here provide additional evidence for cholinergic neurotransmission in the human retina.