[Electron microscopic localization of serotonin acetyl transferase in the pineal body]

Substrat of the hydroxy-indol-O-methyl transferase (HIOMT) N-acetylserotonin is synthesized by serotonin-acetyltransferase. For the demonstration of the localization of this enzyme in the corpus pineale uranyl and cuprum ferrocyanid technique were used. In both cases a mitochondrial localization was revealed. Product of reaction appeared on the outer and inner membranes and in the intracrystal space. The reaction takes place in the presence of Acetyl-Co-A. The cuprumferrocyanid technique seems to have advantages as compared to the uranylferrocyanid method. Extramitochondrial precipitate or aspecific reaction occur seldom.