Biochemical stability of the AChE molecular forms after cytochemical staining: postnatal focalization of the 16S AChE in rat muscle.

A biochemical analysis of rat muscle acetylcholinesterase (AChE) is possible after a cytochemical staining at pH7 (Koelle and Friedenwald method). The solubilization properties, the physicochemical characteristics (sedimentation coefficients) of the multiple molecular forms of AChE are similar before and after the cytochemical procedure without fixation and without ammonium sulfide treatment. This is in contrast to the partial inactivation obtained after conventional pH 5 cytochemical staining, which selectively inactivates 16S AChE. We found that pH 7 cytochemical staining in these same conditions afford a satisfying morphological visualization of the motor end-plate AChE. The combined cytochemical-biochemical techniques allow a very precise dissection of motor end-plate containing (neural) and free (aneural) regions. In rat muscle (sternomastoid), high levels of 16S AChE are present in the aneural region in the first stages of postnatal development. At the end of the 1st month after birth, the 16S AChE becomes restricted to the neural (motor end-plate) region.