Abstract
Abstract
Cadmium metallothionein (CdMT) binds to isolated renal proximal tubular brush border membranes (BBM). The characteristics of this in vitro binding reflect those of the process of CdMT reabsorption in vivo in at least three aspects: (i) two parallel processes are involved in the reabsorption of CdMT in vivo, and two classes of binding sites appear to exist for CdMT on BBM in vitro. Both in vitro and in vivo, the processes differ in their affinity for CdMT. (ii) Myoglobin inhibits the renal reabsorption of CdMT in vivo and the binding of CdMT to isolated BBM. (iii) Reabsorption of CdMT is depressed in rabbits chronically treated with cadmium; isolated BBM from such animals have a decreased ability to bind CdMT. We conclude that the reaction of CdMT with BBM in vitro is the same as that which controls rate and specificity of CdMT reabsorption in vivo.
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