The distribution of esterase in the rat small intestine

A non.specific esterase activity was demonstrated III the jejunum of rats by an azoindoxyl method. 1) Microvilli of the jejunal epithelial cells were remarkably stained in non-frozen specimens and feebly in frozen specimens. 2) The other cytoplasmic structures, i. e. mitochondria, endoplasmic reticulum, nuclear envelope, plasma membrane and multivesicular body showed a positive reaction product in frozen sections but not in non-frozen blocks.