Abstract
We examined the recovery mechanisms of carp(Cyprinus carpio)in response to severe lead poisoning by exposure over 28 and 114 days. Based on the findings, we developed a hypothesis to explain the main defense mechanisms employed by carp. Under conditions of acute lead poisoning using lead concentrations exceeding 1.0 mg/L, the mechanism employed to prevent the absorption of lead in solution through the gill epithelia was the formation of a mucous membrane on the surface of the gills and body, which acted as a ligand for lead. Conversely, for lead concentrations lower than those required to induce acute lead poisoning, carp may prevent lead uptake by hematopoietic organs by elevating production of 5-aminolevulinic acid dehydratase(ALA-D),which has a high affinity for lead, in the erythrocytes. Since this mechanism is thought to occur in conjunction with hemoglobin biosynthesis, the general defense mechanism employed by carp is thought to be a cumulative response using the two aforementioned physiological mechanisms.
