ABSTRACT
The toxicity of methylmercury is sufficiently high to justify an evaluation of the risk from the consumption of contaminated food. In the method of risk assessment proposed here, distribution frequencies are assigned to the parameters in question, rather than mean values. Total body burden is estimated by numerical simulation on a digital computer. Based on recorded cases of incipient intoxication and allowing a safety factor of 10, the critical body burden has been estimated at between 5, 4 and 6 mg total mercury. From an application of this approach to the assessment of risk from Mediterranean red tuna fish consumption, it appears that there may exist high frequency consumers whose body burdens, while not in the overtly neurotoxic range, approach the computed critical level.
Subject(s)
Fishes , Food Contamination , Methylmercury Compounds/toxicity , Tuna , Animals , Humans , Methylmercury Compounds/metabolismABSTRACT
The inhibitory effect of methylmercury on rat liver mitochondrial D 3-hydroxybutyrate deshydrogenase--an enzyme of the inner membrane matrix, which requires lecithin as a cofactor and has thiol residues in the active site--has been investigated. Using a partially purified enzymatic extract, methylmercury inhibition of the reactivation of the apodeshydrogenase by liposomes of lecithin has been studied as a function of lecithin concentration in the incubation medium. Partial reactivation has been observed at a concentration 3 times higher than that needed to reactivate the control. The present studies support the hypothesis that phospholipids are implicated in the mechanism of methylmercury inhibition.
Subject(s)
Hydroxybutyrate Dehydrogenase/antagonists & inhibitors , Methylmercury Compounds/pharmacology , Phospholipids/pharmacology , Animals , Binding Sites , In Vitro Techniques , Male , Membranes/drug effects , Mitochondria, Liver/enzymology , Phosphatidylcholines/pharmacology , RatsABSTRACT
Though environmental biological equilibrium seems to be safeguarded as long as the radiological protection of man is assumed, a number of problems raised by environmental protection are not fully solved. In particular, there occur both macroscopic processes of concentration at some levels of the biological chains, and microlocalization at the cellular, subcellular and molecular levels. The long-term consequences of the non-uniform distribution of the radionuclides should therefore be assessed even if the contamination levels of the physical environment are very low. These aspects are of particular significance with alpha-emitters (plutonium and transplutonium elements), beta-emitters (chiefly tritium) and activation products, some of which are radioisotopes of biologically significant elements. The incidence of these processes is discussed in the light of recent and future developments in nuclear energy. This approach might open new avenues for investigations in environmental radiological protection. The concept of a concentration factor between the environment and the total organism must be supplemented by the concept of a localization and concentration factor at the subcellular level. The significance of the physico-chemical forms of the radionuclides and the parameters likely to modify the characteristics of membranes should be emphasized. Finally, an indication is given on priority measures in the area of investigations of the long-term consequences of low doses on environmental organisms.
