Electrophoretic studies of cholinesterases in brain and muscle of the developing chicken

Abstract

Acrylamide gel electrophoresis of aqueous homogenates from whole brain of perfused chick embryos of 18 days' incubation results in three anodally migrating zones having the properties of cholinesterases (ChE's 1, 2 and 3). These sites hydrolyze acetylthiocholine, alpha-naphthyl acetate and alpha-naphthyl propionate. Their activity is inhibited by 10 −5 M eserine sulfate, by 10 −4 M di-isopropylfluoro-phosphate, and by a 10 −4 M solution of Burroughs-Wellcome compound 284c51j dibromide. Homogenization with 0.1% Triton X-100 selectively increases activity of ChE's 1 and 3, especially the former. The three ChE zones occur in all sub-regions of brain which were examined: optic tectum, medulla, cerebellum, telencephalon, and optic nerve, although activities in the last area are very low. In homogenates of adult brain, ChE 1 (the most rapidly migrating form) is considerably less active, relative to ChE's 2 and 3, than in embryos of 18 days' incubation. Aqueous homogenates of heads of embryos at stages 17–18 (3rd day of incubation) show a weak ChE 2. Inclusion of Triton X-100 in the homogenate results in appearance of all three ChE zones in this tissue. Electrophoresis of blood plasma from embryos of 18 days' incubation produces two zones of activity comparable in mobility and substrate affinity to ChE's 2 and 3 of brain. The relative intensities of the reactions in electrophoretic preparations of the two tissues plus the results from perfused brains indicate that residual blood is not the source for the brain enzymes. Electrophoresis of homogenates of skeletal muscle from embryos of 18 days' incubation produces three zones of ChE activity similar to those of brain. In adult muscle, the ChE's 2 and 3 are present, although less intense, and ChE 1 is not detectable. Electrophoretic preparations of limbs from embryos of stages 20–22 show the fastest migrating ChE (ChE 1) as the predominant form. All three ChE's are detectable in limbs at stages 26–27. The results are discussed in relation to literature in the fields of manometric and microscopic studies of cholinesterases in the developing chicken.