Mast cells are present in epithelial layers of different tissues of the mollusc Anomalocardia brasiliana. In situ characterization of heparin and a correlation of heparin and histamine concentration.

Heparin, other sulphated glycosaminoglycans and histamine were extracted from various dissected organs of Anomalocardia brasiliana, a mollusc from the South Atlantic, and quantified. A good correlation between heparin and histamine content was found in the labial palp, intestine, ctenidium, mantle and foot tissues. The tissue location of metachromatic cells, putatively containing heparin, was identified histologically with Alcian Blue, Toluidine Blue, Masson trichrome, Haematoxylin-Eosin and PAS. Except for the foot, cells containing metachromatic granules were found in the epithelium surfaces of all the organs analysed. An in situ identification of heparin using nitrous acid and heparinase degradation has established unequivocally the presence of this compound in the metachromatic cells. The location of 'mast-like' cells at the epithelium surface of mollusc tissues exposed to the environment are very similar to the distribution of mammalian and other vertebrate mast cells and gives support to the suggestion for a role of mast cells in defense mechanisms.