Acetylcholinesterase in the platelet-megakaryocyte system. II. Structural localization in megakaryocytes of the rat, mouse, and cat.

Acetylcholinesterase (AchE) activity (EC 3.7.1.7) was demonstrated cytochemically in the megakaryocyte (MK) line of differentiation in the red bone marrow of rat, mouse, and cat. Activity was detected in the Golgi complexes of cells considered to be committed MK precursor cells, and was found in Golgi cisterns through all subsequent stages of MK maturation. In the early, basophilic stage of differentiation some MK showed AchE activity in the perinuclear cistern and in a few profiles of the granular endoplasmic reticulum, but reaction was absent from this location at later maturation stages. Concomitantly with the development of the demarcation membrane system, another membrane system appeared; this system consisted of smooth-surfaced, tortuous tubules and narrow cisterns, and it displayed AchE activity through cytoplasmic maturation. In thrombocytogenic MK, the smooth AchE-reacting membranes (SAM) became the AchE-reacting dense tubular system (DTS) of released MK cytoplasm. The MK of the species studied also contained a varying number of AchE-reacting granules (mouse greater than cat greater than rat) which were distinct from alpha-granules.