Cholinesterase activity in rough and smooth brain microsomal membranes.

Abstract

AbstractRat brain cortex was homogenized in 0.25 M or 0.32 M sucrose and sedimented at 10,000 Xg for 20 min. The supernatant was further separated into two subtractions by density gradient centrifugation in Cs+‐containing sucrose. Electron microscopy, RNA/protein and phospholipid/ protein indices showed that one of the subfractions was similar to the rough‐surfaced (R) and the other to the smooth‐surfaced (S) microsomal fractions separated from liver tissue by Dallner (1963). Cholinesterase (ChE) activity was studied by titration. Only 8–13 % of the total ChE activity was recovered in the 10,000 × g supernatant and about 3–6 % in the subfractions. Both the R and S microsomal subfractions displayed ChE activity; however, the S sub‐fraction had about three times as much activity per mg protein as the R subfraction. Activity due to nonspecific cholinesterase was 13 % of the total ChE activity in the R fraction and 7 % in the S fraction when the homogenate was prepared by homogenization with a clearance of 250 urn at 840 rpm. More vigorous homogenization increased the activities. Histochemical staining for AChE and ns. ChE activities revealed reaction product adjacent to both R and S vesicles.