Selenium supplementation during cadmium exposure: Changes in antioxidant enzymes and the ultrastructure of the kidney

Abstract

Cadmium exposure in mice (8 mg Cd as CdCl 2 /kg bw, for 8 weeks, daily oral) resulted in increased cadmium levels in kidney and liver. The level was quite high in kidney (3 times) as compared to liver. However when selenium (0.35 mg Se as Na 2 SeO 3 /kg bw, daily, orally for 8 weeks) was administered concurrently, a significant decrease in cadmium level was seen in kidney and liver.Cadmium exposure resulted in apparent pathological changes in the proximal convoluted tubules (PCT) in kidney at the electron microscopic level. The mitochondria seem to be most severely affected among the cellular organelles. The alterations included swelling and dilation of the organelles. The cristae showed a disorganized architecture. Activities of the antioxidant enzymes glutathione peroxidase (GSH-Px) and catalase in kidney were also significantly inhibited. However, when selenium was co-administered, the structural integrity of the PCT was comparable to the control. The activity of the antioxidant enzymes was also restored to normal levels.This study suggests that cadmium manifests toxic effects by disrupting the antioxidant enzyme system, which in turn affects the membranous structures such as mitochondria and endoplasmic reticulum. This, in turn, affects the oxidative phosphorylation. Further, it is observed that the co-administration of selenium diminishes the effects of cadmium.

Protective Effect of Seleno-l-Methionine on Cyclophosphamide-Induced Urinary Bladder Toxicity in Rats

“…Moreover, Se has protective effects against mercury toxicity in rat kidney and Se also used to diminish the toxic effects of the cadmium on the antioxidant enzyme system, which in turn affects the membranes structures such as mitochondria and endoplasmic reticulum. On the other hand, Se deficiency reducing GPx activity has been reported in diet of glomerular disease and in diet of tubular epithelium in normal rats [32]. Concurrent or prior injections of Se were found to protect against many of the acute effects of cadmium, e.g., testicular necrosis, placental hemorrhage, teratogenecity, and damage to the lactating mammary glands [14-16, 18-31, 33].…”

Cadmium and Selenium Interaction in Mammals

“…Prema dužini primjene Se i Cd opisana su istraživanja s kroničnim (23,(60)(61)(62)(63), supkroničnim (45,64,65) i akutnim izlaganjima (59,66,67), a rezultati se razlikuju prema učinku Se na distribuciju Cd u unutrašnjim organima.…”

“…Stoga su u novijim istraživanjima međudjelovanja Cd i Se životinje češće izlagane hranom i/ili vodom tijekom dužeg razdoblja (60,62,63 (61,80), povišenja (56,78) ili nepromijenjene razine Cd (60,62,67,77,79,81,82) u odnosu na životinje izložene samo Cd. U našim istraživanjima, u uvjetima peroralne suplementacije Se uz izlaganje Cd, našli smo sniženje Cd u krvi, jetri i bubregu sisajućih štakora (48).…”

“…Glutation peroksidaza dio je glutationredoks-ciklusa koji uklanja slobodne radikale pa se zato suplementacijom Se poboljšava antioksidativni status organizma. Prema rezultatima iz literature, suplementacija Se uglavnom ne utječe na aktivnost KAT uz istodobnu izloženost Cd u odnosu na aktivnost pri izloženosti samo Cd (61,66,67,100). U srcu, slezeni i jetri riba Se je povećao aktivnosti GSH-Px, SOD i KAT, inače smanjene zbog izloženosti Cd, do vrijednosti bliskih kontrolnim vrijednostima (97).…”

“…Slično tomu, Magos i Webb našli su povišenje razina Se u tkivima životinja akutno izloženih ekvimolarnim dozama Cd i Se (46) dok u istraživanju pri kroničnoj izloženosti Se u vodi, nakon supkutane injekcije Cd, nisu nađene značajne promjene u razini Se u jetri, bubrezima, testisima i srcu štakora (126). U nekim istraživanjima nađene su povišene razine Se u jetri i bubregu odraslih životinja istodobno kronično izloženih Se i Cd u odnosu na one izložene samo Se (61,62,79), dok drugi autori nisu našli takve promjene u bubrezima (77,81). U plazmi, mozgu i bubregu sisajućih štakora istodobno izloženih Se i Cd tijekom 9 dana Lazarus i sur.…”