Differences in chromatographic behaviour of rat and pig metallothionein isoforms: a possible method of distinguishing between exogenous and endogenous metallothioneins.
Part of the exogenous metallothionein present, e.g., in food of animal origin, can survive gastrointestinal digestion, and will be selectively taken up in the kidneys. The present paper describes a possible method of distinguishing exogenous cadmium metallothionein (CdMT) from its endogenous counterpart. Rat and pig metallothionein were purified from liver and kidneys of animals previously injected with cadmium chloride. In rats cadmium was present in two MT isoforms, RMT-1 and RMT-2. Ion-exchange chromatography of porcine liver cytosol also showed that two isoforms existed, but a major portion of the cadmium elutes with the second isoform, VMT-2. Using a reversed-phase HPLC system, the purified rat metallothionein isoforms eluted as single peaks before pig MT isoform VMT-2. The difference in chromatographic behaviour on reversed-phase HPLC between species-specific metallothioneins offers a unique possibility to study the fate of endogenous and exogenous metallothioneins simultaneously. This will be illustrated by the redistribution of 109Cd from exogenous CdMT to endogenous CdMT after intravenous injection of VMT-2 into rats.
Groten
J P
JP
Department of Biological Toxicology, TNO Toxicology and Nutrition Institute, Zeist, The Netherlands.
Hissink
E
E
van Bladeren
P J
PJ
D000818:Animals; D002104:Cadmium / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D007668:Kidney / Q000737:chemistry / Q000378:metabolism; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D008668:Metallothionein / Q000302:isolation & purification* / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D013045:Species Specificity; D013237:Stereoisomerism; D013552:Swine
C004203:cadmium-binding protein; D002104:Cadmium; D008668:Metallothionein