Electron microscopic demonstration of phospholipase B activity in the liver and the kidney of the mouse.

A method has been developed for electron microscopic histochemical demonstration of phospholipase B, (lecithinase B, E C 3.1.1.5, lysolecithin acyl hydrolase), which hydrolyzes alpha- and beta-positions of phospholipids in mouse liver, kidney and adrenal tissues. Tissues either fixed in cold 1% paraformaldehyde or unfixed were cut into 40 micrometers frozen sections and were incubated at 37 degrees C in a medium at pH 6.6 or 4.5 containing 2 microM lysolecithin and 0.25 mM CaCl2 for 20 min. The fatty acids liberated by enzymatic hydrolysis were trapped as calcium precipitate and were converted to lead precipitate by treatment with lead nitrate. The reaction products were observed by electron microscopy to be localized on the end of the smooth endoplasmic reticulum at pH 6.6 and in lysosomes and lipid droplets at pH 4.5. It is concluded that the products showed the localization of phospholipase B activity.