Wf. Tang et al., NEPHROTOXICITY OF CADMIUM-METALLOTHIONEIN - PROTECTION BY ZINC AND ROLE OF GLUTATHIONE, Toxicology and applied pharmacology, 151(2), 1998, pp. 276-282
Chronic cadmium (Cd) exposure can cause renal proximal tubular dysfunc
tion resulting from the release of Cd metallothionein (CdMT) from the
liver and its accumulation and degradation in the renal tubular epithe
lial cells. Pretreatment with zinc (Zn) can protect against acute CdMT
nephrotoxicity. While induction of MT by Zn plays a part in Zn protec
tion, other factors, such as glutathione (GSH), may also be involved b
ecause protection is offered even in MT-null mice. The present study w
as designed to investigate the involvement of GSH in Zn protection aga
inst acute CdMT nephrotoxicity. The study was carried out in MT-null m
ice to remove the induction of MT by Zn as a confounding variable. Thr
ee approaches were used to modulate renal cortex GSH levels: buthionin
e sulfoximine (BSO) was administered to inhibit GSH synthesis, and GSH
and Zn were administered to increase the GSH levels. Both GSH and Zn
were effective in protecting against CdMT nephrotoxicity. Elevation in
renal cortex GSH levels, however, was not essential for Zn protection
, as a low dose of Zn that caused no significant increase in renal GSH
also protected against CdMT. On the other hand, maintenance of normal
GSH status was essential for Zn protection, as inhibition of GSH synt
hesis abolished this protection. Both GSH and Zn reduced the accumulat
ion of Cd as well as MT in the renal cortex, with Zn causing greater r
eduction in Cd accumulation than that of MT. The relative intracellula
r distribution of Cd was unaltered. These results suggest that in MT-n
ull mice Zn protects against CdMT nephrotoxicity by possibly displacin
g some of the Cd from CdMT as well as reducing the uptake of CdMT, and
that this protection requires the maintenance of normal GSH status, (
C) 1998 Academic Press.