Human retinas synthesize and release acetylcholine.
Human retinas have the capacity to synthesize and release [3H]acetylcholine ([3H]ACh) after an incubation in [3H]choline ([3H]Ch). Synthesis of [3H]Ch by retinal homogenates was determined using either high-voltage paper electrophoresis (HVPE) or a two-step enzymatic/extraction assay for separating [3H]ACh from [3H]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 [3H]ACh from [3H]Ch. We find an approximate Km of 50 microM and a Vmax of about 20 nmol/mg protein/h (at 37 degrees C) for the synthesis of labeled ACh by retinal homogenates. Human retinas also release [3H]ACh after a pulse of [3H]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.
J B
JB
Hutchins
J G
JG
Hollyfield
D000109:Acetylcholine / Q000096:biosynthesis* / Q000378:metabolism; D002794:Choline / Q000378:metabolism; D004590:Electrophoresis, Paper / Q000379:methods; D006801:Humans; D066298:In Vitro Techniques; D008722:Methods; D012160:Retina / Q000378:metabolism*; D014316:Tritium
D014316:Tritium; D002794:Choline; D000109:Acetylcholine