HISTOCHEMISTRY OF RAT NEUROHYPOPHYSEAL PITUICYTE LIPID GRANULES: AUTOXIDATION OF UNSATURATED FATS DURING FIXATION

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Abstract
Osmiophilic granules contained in neurohypophysis pituicytes of the rat are made of unsaturated neutral lipids undergoing, during the fixation in formalin, a process of autoxidation. This process is characterized by the transitory appearance of hydroperoxide radicals while the double bonds decrease more and more until they disappear; is accompanied by the decrease of the osmium tetroxide and dichro-mate acid haematein stainability, while acid groups appear determining the conversion from pink to blue of Nile blue stain. This process is prevented by adding an antioxidant to the formalin and is absent after fixation in potassium dichromate.