ACETYLCHOLINE AND ACETYLCHOLINESTERASE ACTIVITY IN EARLY EMBRYOS OF THE MEDAKA ORYZIAS LATIPES, A TELEOST

Abstract

Acetylcholinesterase (AChE) activity is present in homogenates of medaka [O. latipes] embryos during cleavage and epiboly. Levels of AChE activity change little during this period of development and are similar in embryos grown at 15 or 25.degree. C. Specific activity of AChE in cells isolated from blastulae is 0.06 mmol substrate hydrolyzed/min per g protein, a value comparable to that of chicken myoblasts and myotubes in vitro. AChE activity was detected cytochemically in all cells dissociated from blastulae and grastrulae. In deep blastomeres AChE activity is present nearly throughout the cytoplasm; it is absent from peripheral regions of the cytoplasm which are involved in circus or limnicolor, movements. Acetylcholine-like activity in extracts of embryos was assayed. The active principle was inactivated by heating at pH 10 and by incubation at pH 7.0 with commercial AChE. The active principle migrated on Whatman # chromatography paper with the same Rf as authentic acetylcholine in 3 solvent systems. The amount of acetylcholine in blastulae is about 4 pmol/embryo.