Ultracytochemical analysis of cytoplasmic lipids by enzymic digestive methods

Both floating Vibratome sections from the following organs of rats, fixed in vivo by vascular perfusion; early and recovery stages of ethionine-induced fatty liver, secreting mammary gland, Gentamicin-injured renal cortex and resting adrenal cortex, and intact red cells of guinea pigs suspended in an isotonic buffer were treated, respectively, with the digestion medium containing each one of the following esterases; mold lipase, snake venom phospholipase and cholesterol esterase from microorganism. After digestion, the samples were immersed in 0.05-0.1% Pb(NO3)2, fixed in osmium buffer, dehydrated by Idelman's procedure, and finally embedded in epon. The derived fatty acids through enzymic digestions were detected in ultrathin sections as lead soaps, which were never seen in the duplicate control sections. Such a developed lead soap after digestion should indicate the location of substrate. This technique might be useful for the qualitative analysis of some mixedphased lipids in ultrastructure.