MECHANISMS OF HEAVY-METAL CATION HOMEOSTASIS IN MARINE-INVERTEBRATES

1. The main mechanisms involved in heavy metal cation homeostasis in m arine invertebrate cells are described. 2. Metallothioneins are probab ly the most important soluble compounds involved in heavy metal cation homeostasis. The biochemical characteristics of these metalloproteins and the relationship between their amino acid composition and heavy m etal binding capacity are elucidated. Moreover data are reported conce rning the physiological role of metallothioneins e.g. heavy metal deto xification, cellular metal redistribution, free radical scavenger acti on, etc. The possible meaning of different soluble compounds in heavy metal cation homeostasis is also discussed. 3. The biochemical role of lysosomes in heavy metal cation compartmentalization and the involvem ent of these organelles in metallothionein accumulation and sequestrat ion are shown. 4. Data are reported concerning the sequestration of he avy metal cations in insoluble granules as a mechanism of metal detoxi fication.