Histochemical and biochemical demonstration of the molecular forms of acetylcholinesterase in peripheral nerve of rat.

The molecular forms of AChE and their ultrastructural localization in the sciatic nerve and spinal ganglion were studied biochemically and histochemically. Our results suggest that the histochemical end-products due to the AChE activity are present in the cisternae of the RER of the perikaryon (4S,C form). The 6S,C and 10S,B' forms can be found in tubules and in vesicles inside the axon, while the 10S,B form may be present bound on the outer surface of the axolemma. The 16S,A form is localized in some intraaxonal cell organelles during transport. From the results presented it is inferred that the AChE from the perikaryon is transported both free in the cytoplasm and sequestered in a soluble form inside the tubules and vesicles, where a part of it is converted to the 10S,B' and 16S forms. When the AChE-active tubules are joined to the surface membranes, the 10S,B' form may be "extruded" (secreted) and bound to the outer surface of the unit membrane (10S,B form). Since both the 10S,B' and 16S forms are present in the tubules and vesicles, the regulatory process involved in the distribution of the 10S,B' AChE to the axon surface and of the 16S,A form to the axon terminal must be further examined.