Record Details
Mercury and cadmium binding proteins in marine mammal tissues
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | Mercury and cadmium binding proteins in marine mammal tissues |
| Names |
von der Trenck, Karl Theodor
(creator) Buhler, D. R. (advisor) |
| Date Issued | 1975-11-17 (iso8601) |
| Note | Graduation date: 1976 |
| Abstract | The subcellular fractions of liver and kidney from three bearded seals (Erignathus barbatus nauticus) and three walrus (Odobenus rosmarus divergens) were analyzed for cadmium and mercury content, and the results were compared with the results of subcellular fractionation of the same organs from two sea lions (Zalophus callfornianus californianus) obtained previously in our laboratory (Lee et al. , 1976). When the heavy metal concentration in the cytosol was plotted against that in the whole cell, evidence for two phases of accumulation of heavy metals in the cytosol was obtained. At low cellular concentrations, proportionally more heavy metal was found in the cytosol than at higher concentrations. Under these latter conditions, cadmium had accumulated in the cytosol to a lesser degree, while mercury concentration remained constant. The soluble fractions of kidney and liver from two bearded seals and three walrus were chromatographed on Sephadex G-75 and cadmium and mercury distribution among proteins of different molecular weight was determined. Similar results for two sea lions (Lee et al. , 1976) were compared with the ones for the arctic marine mammals. At low concentrations of heavy metals in the cytosol, the amount of metals in metallothionein was related much closer to that in the cytosol than at higher concentrations, where a very limited degree of linear correlation was observed. Two types of heavy metal binding sites with different affinities are a likely explanation for these biphasic distribution curves. Mercury thus showed a distinct tendency to accumulate in the particulate fractions and the soluble proteins of high molecular weight, whereas cadmium was found much more in the soluble and metallothionein fractions. Liver was recognized as the main organ to deposit mercury and kidney as a major site for cadmium accumulation in all three species. Nevertheless, the same general principle(s) appeared to govern heavy metal distribution in both organs. A search in sea lion liver for a soluble protein of high molecular weight that binds mercury specifically failed to demonstrate such a protein, but showed that mercury binds nonspecifically to a great number of soluble proteins of around 150, 000 daltons. Use of a specific assay to measure metallothionein levels in livers and kidneys of three bearded seals, three walrus, and three sea lions revealed a very low degree of linear correlation between metallothionein content and heavy metal concentration. Only cadmium levels in the kidney cytosol were correlated to some extent (R²=0. 56) with the amounts of metallothionein found in the same organs. These results are inconsistent with the induction of metallothionein by high heavy metal concentrations in marine mammals. The 10, 000 x g supernatant of sea lion liver homogenate containing an active mixed function oxidase system was found to catalyze the demethylation of added methylmercury in vitro at a rate of 22% in 16. 5 h. |
| Genre | Thesis/Dissertation |
| Topic | Marine mammals -- Mercury content |
| Identifier | http://hdl.handle.net/1957/44830 |
