ACETYLCHOLINESTERASE AND BUTYRYLCHOLINESTERASE ACTIVITIES IN THE RAT RETINA AND RETINAL-PIGMENT EPITHELIUM

The acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activ ities in the neural retina and retinal pigment epithelium (RPE) of adu lt rats were determined, The tissues were extracted with a saline buff er to release the soluble enzymes (S-1) and the pellet re-extracted wi th Triton X-100 to detach the membrane-bound enzymes (S-2). Less than 5% of the cholinesterase activity measured in retina and almost 30% of that assayed in RPE was due to BChE. About 20% and 10% of the AChE in retina and RPE was brought into solution with a saline buffer and the rest with a detergent-containing buffer. Main AChE molecular forms of 10.5S (hydrophilic G(4)(H)), 9.5S (amphiphilic G(4)(A)) and 3.0S (amp hiphilic G(1)(A)) were identified in retina by subjecting the supernat ant S-1 to sedimentation analysis in sucrose gradients made with Brij 96. Amphiphilic G(4) and G(1) AChE were found in S-2. Analysis of the soluble fractions obtained from RPE in the gradients made with Brij 96 revealed 16.0S (asymmetric A(12)), 10.5-10.0S (globular G(4)(H) + G(4 )(A)), 4.5S (G(2)(A)), and 3.0S (G(1)(A)) AChE forms in S-1, whereas G (4)(A) G(2)(A), and G(1)(A) enzyme molecules predominated in S-2. Our results show that amphiphilic tetramers and monomers of AChE are abund ant in neural retina, and enzyme tetramers, dimers, and monomers in RP E. The AChE in the neural retina might be involved in cholinergic acti ons. epithelium remains to be established. (C) 1995 Wiley-Liss, Inc.