CHARACTERIZATION OF ACETYLCHOLINESTERASE SECRETION IN NEURONAL CULTURES AND REGULATION BY HIGH K-CELLS( AND SOLUBLE FACTORS FROM TARGET)

We have observed that cultured neurons from chick spinal cord and the neuroblastoma hybrid line 108CC15 released lower amounts of acetylchol inesterase (AChE) when compared with the parental line, N18TG2. AChE a ctivity extracted by hypotonic buffer, which can be regarded as the so urce of the released enzyme, was considerably higher in the parental t han in the hybrid 108CC15 (respectively, similar to 80% and similar to 40% of cellular activity). On the other hand, evaluation of ectocellu lar, with respect to total, AChE activity showed that in N18TG2 cells only 7% of AChE was localized on the plasmalemma, whereas in the hybri d line the percentage of ectocellular activity was 3.7 times higher th an in the parental line. We have also examined the effect of cytochala sin B and nocodazole. In the N18TG2 line. the former did not affect AC hS release, which was significantly reduced by the tatter. High K+ lev el in the culture medium, of both N18TG2 and hybrid 108CC15 cultures, induced an increase in AChE secretion; Ca2+ presence was required for high K+-induced release. Muscle extracts increased AChE secretion in b oth the hybrid 108CC15 and the spinal cord neurons. The present data s uggest that AChE secretion during neuronal development is modulated by depolarizing stimuli and by soluble factors produced by target cells and may be involved in the control of neuronal differentiation.