ACTIVITY OF ACETYLCHOLINESTERASE AND UNSPECIFIC CHOLINESTERASE DURINGDIFFERENTIATION OF SOMITES IN MOUSE EMBRYOS

During the development of somites in mouse embryos, widespread activit y of unspecific cholinesterase (BuChE) was demonstrated after prolonge d incubation. Independent of their position, all somite cells and thei r derivatives (dermatome, myotome and sclerotome) exhibited enzyme act ivity in the perinuclear space and in the endoplasmic reticulum. The p lasmalemma did not show any enzyme activity. Differentiation of the sc lerotome into vertebrae was accompanied by a reduction of BuChE. Howev er, a low enzyme reaction was still present in the first typical diffe rentiated chondroblasts. Notochordal cells were detectable by their hi gh BuChE content. This was also found in cells already showed severe d egeneration. In addition to BuChE, acetylcholinesterase (AChE) was fir st visible on day 9 of embryonic development in newly formed myotubes of the myotomes. Some hypotheses on the functional significance of emb ryonic BuChE are discussed in the light of these results.