Heavy metal binding properties of earthworm chloragosomes
Ireland, M.P.
Acta Biologica Academiae Scientiarum Hungaricae 29(4): 385-394
1978
ISSN/ISBN: 0001-5288 PMID: 757448 Document Number: 130197
The highest concentration of metal in Lumbricus terrestris and L. rubellus chloragosomes was Ca2+ followed by Fe3+, Zn2+ and Mg2+. Chloragosomes and body wall extracts bound Pb2+ and to a lesser extent Cu2+ but not Zn2+. Binding of Pb2+ and Cu2+ was greater in chloragosomes than body wall homogenate. Maximum binding capacity for Pb2+ was higher in L. terrestris than L. rubellus. The binding of Pb2+ to chloragosomes appears to be unrelated to phospholipid content. The release of most Zn2+ and Ca2+ in chloragosomes by 0.01 M HCl but release of Fe3+ requiring 5 M HCl suggests that the latter may be in the form of an organometallic complex. Release of Cu2+ from chloragosomes by 0.001 M HCl but only 20% of the bound Pb2+ indicates that Pb2+ is more firmly bound to chloragosomes than Cu2+. Bound Pb2+ in body wall extracts is released by 0.001 M HCl. The addition of Pb2+ to a chloragosomal suspension caused a drop in pH and release of mainly Ca2+ with smaller amounts of Zn2+ and Mg2+ indicating a cation exchange was taking place. Earthworm chloragosomes bind heavy metal by a cation exchange system which may be related to the chemical constituents of chloragosomes being similar to ion exchange compounds.