Distribution of acetylcholinesterase and butyrylcholinesterase in the myenteric plexus and longitudinal muscle of the guinea-pig intestine

Manometric analyses of the hydrolysis of various choline esters and the effects upon it of selective anticholinesterases showed that in blood-free homogenates of plexus-containing longitudinal muscle sheets detached from guinea-pig small intestines two enzymes were present, a typical acetylcholinesterase (AChE) and a typical butyrylcholinesterase (BuChE). Homogenization did not release into solution all the AChE or BuChE, as demonstrated by the finding that after centrifugation activity was present not only in the supernatant fractions but also in the sediments. The mechanical removal of Auerbach's plexus led to a 76·3 ± 3·3 per cent decrease in AChE content but reduced the BuChE content only by 10·6 ± 9·3 per cent, as assessed by the hydrolysis of dl-acetyl -β-methylcholine and n-butyrylcholine, respectively. Since dl-acetyl-β-methylcholine is also hydrolysed slowly by BuChE the decrease in AChE content could be even greater, by another 10 per cent. In the ascending and transverse colon the contents of AChE and BuChE in the plexus-containing longitudinal muscle were lower than those found in the small intestine. The loss of Auerbach's plexus reduced the AChE content by 57·4 ± 3·0 per cent, without change in BuChE content. Small regional differences in the content of AChE but not of BuChE were detected in the longitudinal muscle of the small intestine.