The Mechanism of Accumulation of Vanadium by Ascidians: Some Progress towards an Understanding of this Unusual Phenomenon
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概要
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Since the discovery of vanadium in the blood cells (coelomic cells) of an ascidian by Henze in 1911, this unusual phenomenon has attracted the interest of many investigators. We started our studies by examining the vanadium contents of several tissues from 20 ascidian species, collected not only from Japanese waters but also from the Mediterranean since about 18 years ago, using an extremely sensitive method, namely, neutron-activation analysis. We found the highest concentration of vanadium, 350 mM, in the blood cells of Ascidia gemmata which belongs to the suborder Phlebobranchia. This concentration of vanadium is 10^7 times higher than that in seawater. Among the approximately ten types of blood cells, the signet ring cells were revealed to be the true vanadocytes by a combination of cell fractionation and neutron-activation analysis. Of the vanadium in these vanadocytes, 97.6% was in the +3 oxidation state while the rest was in the +4 oxidation state. The contents of the vanadocytes in A. gemmata had a low pH of 2.4 and these cells contained the highest levels of vanadium. These observations suggested the possibility that protons, concentrated by a H^+-ATPase, might be linked energetically to the accumulation of vanadium. Antibodies raised against a vacuolar-type H^+-ATPase were found to react with the vacuolar membranes of signet ring cells and the addition of bafilomycin A_1, a specific inhibitor of vacuolar-type H^+-ATPases, inhibited the uptake of protons by the vacuoles of signet ring cells, with resultant neutralization of the contents of the vacuoles. A monoclonal antibody, S4D5, prepared for the purpose of identifying signet ring cells, reacted with the signet ring cells not only of A. sydneiensis samea, which had been used as the antigen, but also with those of other species. During embryogenesis, a vanadocyte-specific antigen, recognized by this monoclonal antibody, appeared for the first time in the body wall at the same time as the significant accumulation of vanadium became apparent. Characterization of vanadium-binding proteins extracted from the blood cells of vanadium-rich ascidians is in progress and shows to help us determine the way in which ascidians selectively accumulate high levels of vanadium from seawater. The unusual phenomenon whereby some ascidians accumulate vanadium to levels more than ten million times higher than those in seawater has attracted the interest of researchers in various fields. Studies of ascidians with this unusual physiological property may help us to clarify not only how ascidians but also other organisms accumulate transition metals, as well as the physiological roles of these metals.
- 社団法人日本動物学会の論文
- 1996-08-15
著者
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Michibata Hitoshi
Mukaishima Marine Biological Laboratory Faculty Of Science And Laboratory Of Marine Molecular Biolog
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Michibata Hitoshi
Mukaishima Marine Biological Laboratory Faculty Of Science And Laboratory Of Marine Molecular Biolog
関連論文
- Isolation of cDNAs Encoding Subunits A and B of the Vacuolar-Type ATPase from the Vanadium-Rich Ascidian, Ascidia sydneiensis samea(Physiology)
- A 100-kDa Antigen Recognized by a Newly Prepared Monoclonal Antibody Specific to the Vanadocytes of the Vanadium-Rich Ascidian, Ascidia sydneiensis samea, is Glycogen Phosphorylase(Physiology)
- Glucose-6-Phosphate Dehydrogenase in the Pentose Phosphate Pathway Is Localized in Vanadocytes of the Vanadium-Rich Ascidian, Ascidia sydneiensis samea
- Specific Increase in the Number of Vanadium-Containing Blood Cells by Some Ionophores and Inhibitors of Proton-ATPases in the Ascidian, Ascidia sydneiensis samea
- Finding of the Same Antigens in the Polychaete, Pseudopotamilla occelata, as Those in the Vanadium-Rich Ascidian, Ascidia sydneiensis samea
- Identification of a Vanadium-Associated Protein from the Vanadium-Rich Ascidian, Ascidia sydneiensis samea
- Localization, with Monoclonal Antibodies and by Detection of Autonomous Fluorescence, of Blood Cells in the Tissues of the Vanadium-Rich Ascidian, Ascidia sydneiensis samea
- Preparation and Localization of a Monoclonal Antibody against a Vanadium-Associated Protein Extracted from the Blood Cells of the Vanadium-Rich Ascidian, Ascidia sydneiensis samea
- Reduction of Vanadium(IV) to Vanadium(III) by Cysteine Methyl Ester in Water in the Presence of Amino Polycarboxylates
- The Mechanism of Accumulation of Vanadium by Ascidians: Some Progress towards an Understanding of this Unusual Phenomenon
- THE MECHANISM OF ACCUMULATION OF METALS, ESPECIALLY HIGH LEVELS OF VANADIUM, BY ASCIDIANS