Cytochemical localization of adenylate cyclase activity in rat bone marrow

The localization of adenylate cyclase (AC) in rat bone marrow was studied at the ultrastructural level using a cytochemical technique with adenosine triphosphate (ATP) as substrate. The strongest precipitate occurred around cytoplasmic membranes of cells of granulocytic lineage. Around cells of erythrocytic lineage, as well as megakaryocytes, lymphocytes and the plasma cells, the granules resulting from the cytochemical reaction revealed various degrees of density. The region within the bone marrow tissue where the cells manifested an increased reaction product was called 'reaction fields'. Most often the 'reaction fields' were formed by maturing cells of the granulocytic and erythrocytic lineages, surrounding the reticular cells. The reaction precipitate was also apparent around the advential and endothelial cells of the sinuses. Mature cells migrating from the bone marrow space to the sinus lumen also showed an intensified reaction product. The causes of such localization of AC were discussed.