THE ELIMINATION OF ENZYMATIC DIFFUSION ARTIFACTS IN THE HISTOCHEMICAL LOCALIZATION OF CHOLINESTERASES AND A SURVEY OF THEIR CELLULAR DISTRIBUTIONS

¹ Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York 32, New York

1. Histochemical studies using thin (10 micra) fresh frozen sections indicated the occurrence of artifacts of localization of ChE's with a previously published method as the result of enzymatic diffusion; confirmatory evidence of such was obtained by manometric measurements of the ChE activities of liver homogenates and isolated nuclei.

2. By means of recovery tests, it was found that purified specific (bovine erythrocyte) and non-specific (horse serum) ChE's were practically completely precipitated at pH 6.0 in the presence of 20 and 24 per cent Na₂SO₄, respectively. Crude preparations of cat specific and non-specific ChE's were completely recovered following precipitation at pH 6.0 with 24 and 28 per cent Na₂SO₄, respectively. The effects of precipitation by Na₂SO₄ on the activities of the enzymes were determined.

3. The earlier histochemical method was modified in accordance with the foregoing findings and by certain minor changes to eliminate enzymatic diffusion artifacts and to enhance the accuracy of the cellular localizations of the ChE's.

4. Specific ChE activity was found principally in the dendrites, cell bodies, axons and terminations of cholinergic neurons (anterior and lateral horn cells, certain autonomic ganglion cells), at the motor endplates of striated muscle, and in low concentrations in sensory neurons (dorsal root and nodose ganglion cells.)

5. Non-specific ChE activity was localized in the capsular glial cells of sensory and autonomic ganglion cells, in certain Schwann's sheath cells, in groups of chemoreceptor cells, in the cells lining the sinusoids of the liver, and in the smooth muscle fibers, stellate cells and occasional ganglion cells of the ileum.

6. Physiological implications of the present findings are discussed, particularly in regard to the probable roles of ACh and the ChE's in conduction and transmission.

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