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Effect of dietary vitamin E on ferric nitrilotriacetate-induced nephrotoxicity in rats
TOXICOLOGY
AND
APPLIED
PHARMACOLOGY
92,500-506
(1988)
Effect of Dietary Vitamin E on Ferric Nitrilotriacetate-Induced Nephrotoxicity in Rats Effect of Dietary Vitamin E on Ferric Nitrilotriacetate-Induced MAZAKI,
S., ORADA,
S.,
EBINA,
Y.,
LI,
J.-L.,
AND
MIDORIKAWA,
Nephrotoxicity 0. (1988).
in Rats. HAToxicol.
Appl.
92,500-506. The effect ofdietary vitamin E on renal tissue damage and lipid peroxidation was investigated following treatment with ferric nitrilotriacetate (Fe-NTA) in rats. Almost 100% renal proximal tubular necrosis was observed in the vitamin E-deficient rats following Fe-NTA treatment (5 mg Fe/kg body wt, ip) as early as 12 hr. In the vitamin E-supplemented rats, no injury was observed in the proximal convoluted (cortical) tubules, although some injury was seen in the medullary outer stripe (mostly pars recta of the proximal tubules) 24 hr after FeNTA treatment. The tissue lipid peroxidation was dose-dependently increased 1 hr after a single ip injection of Fe-NTA (1 to 10 mg Fe/kg body wt). Vitamin E-deficient animals had an increased tissue content of thiobarbituric acid-reactive substance following Fe-NTA treatment, whereas vitamin E-supplemented animals showed suppressed lipid peroxidation. This study indicates that vitamin E provides some protection against the nephrotoxicity and associated lipid peroxidation induced by Fe-NTA. o 1988 Academic press, IK. Pharmacol.
Nitrilotriacetate (NTA) is an effective chelating agent that has been used as a detergent builder in several countries. Microscopic renal tubular alterations and a low incidence of urinary-tract tumors have been reported in experimental animals fed high concentrations of noncomplexed NTA (Anderson et al., 1985). As the metal ion/NTA formation constant is high, NTA exists as a metal complex in a near neutral or basic environment. The ferric chelate of NTA (Fe-NTA) was reported to cause glucosuria in rats, whose liver morphology was indistinguishable from idiopathic hemochromatosis in man (Awai et al., 1979). We reported the development of glucosuria and aminoaciduria following renal tubular necrosis and a high incidence of renal adenocarcinoma in rats and mice treated with repeated ip injections of Fe-NTA (Ebina et al., 1986; Li et al., 1987; Okada and Midorikawa, 1982). The toxicity associated with excessive iron intake is thought to be a result of increased lipid peroxidation in the membrane (Jacobs, 1980). In the present study, the effect of vitamin E, a physiological membrane radical scavenger (Witting, 1980), on the renal tubular damage and lipid peroxidation caused by Fe-NTA treatment was examined. 0041-008X/88
$3.00
Copyright 0 1988 by Academic Press. Inc. All rigbts of reproduction in any form reserved.
MATERIALS
AND
METHODS
Animals and Fe-NTA administration. Weanling male Wistar rats (Shizuoka Laboratory Animal Center, Shizuoka) were given standard rat chow (Funahashi-nojo, Chiba) or a synthetic basic diet with or without vitamin E supplement (Oriental Yeast, Tokyo). The basic diet without vitamin E supplement is referred to as a vitamin E-deficient diet, and those containing 20 mg/kg diet of DL-a-tocopheryl acetate and 585 mg/kg diet of DL-a-tocopheryl nicotinate are referred to as a vitamin E-sufficient and vitamin E-supplemented diets, respectively. Rats were given ip injections of Fe-NTA solution which were prepared as previously described (Awai et al., 1979). Some of the rats were given noncomplexed NTA (168 mg/kg body wt, ip), which was considered to be equivalent to the NTA portion of the Fe-NTA dose at 10 mg Fe/kg body wt. The experimental groups, their diets and their Fe-NTA doses are shown in Table 1. Rats were killed by decapitation and the kidneys were quickly excised and processed for histologic study or lipid peroxidation assay. Light microscopy. The tissues were processed routinely and stained with hematoxylin and eosin. The renal cortex, where most of the proximal tubules belong to the pars convoluta, and the medullary outer stripe, where the straight portion of the proximal tubules is dominant, were separately analyzed. The percentage of tubules showing cell fragmentation and karyorrhexis was determined by light microscopy under low-power magnification (X100). Five to ten fields were evaluated in each measurement. Determination of lipid peroxidation. All the reagents were of the highest quality avaiable and obtained from
500
AND
APPLIED
PHARMACOLOGY
92,500-506
(1988)
Effect of Dietary Vitamin E on Ferric Nitrilotriacetate-Induced Nephrotoxicity in Rats Effect of Dietary Vitamin E on Ferric Nitrilotriacetate-Induced MAZAKI,
S., ORADA,
S.,
EBINA,
Y.,
LI,
J.-L.,
AND
MIDORIKAWA,
Nephrotoxicity 0. (1988).
in Rats. HAToxicol.
Appl.
92,500-506. The effect ofdietary vitamin E on renal tissue damage and lipid peroxidation was investigated following treatment with ferric nitrilotriacetate (Fe-NTA) in rats. Almost 100% renal proximal tubular necrosis was observed in the vitamin E-deficient rats following Fe-NTA treatment (5 mg Fe/kg body wt, ip) as early as 12 hr. In the vitamin E-supplemented rats, no injury was observed in the proximal convoluted (cortical) tubules, although some injury was seen in the medullary outer stripe (mostly pars recta of the proximal tubules) 24 hr after FeNTA treatment. The tissue lipid peroxidation was dose-dependently increased 1 hr after a single ip injection of Fe-NTA (1 to 10 mg Fe/kg body wt). Vitamin E-deficient animals had an increased tissue content of thiobarbituric acid-reactive substance following Fe-NTA treatment, whereas vitamin E-supplemented animals showed suppressed lipid peroxidation. This study indicates that vitamin E provides some protection against the nephrotoxicity and associated lipid peroxidation induced by Fe-NTA. o 1988 Academic press, IK. Pharmacol.
Nitrilotriacetate (NTA) is an effective chelating agent that has been used as a detergent builder in several countries. Microscopic renal tubular alterations and a low incidence of urinary-tract tumors have been reported in experimental animals fed high concentrations of noncomplexed NTA (Anderson et al., 1985). As the metal ion/NTA formation constant is high, NTA exists as a metal complex in a near neutral or basic environment. The ferric chelate of NTA (Fe-NTA) was reported to cause glucosuria in rats, whose liver morphology was indistinguishable from idiopathic hemochromatosis in man (Awai et al., 1979). We reported the development of glucosuria and aminoaciduria following renal tubular necrosis and a high incidence of renal adenocarcinoma in rats and mice treated with repeated ip injections of Fe-NTA (Ebina et al., 1986; Li et al., 1987; Okada and Midorikawa, 1982). The toxicity associated with excessive iron intake is thought to be a result of increased lipid peroxidation in the membrane (Jacobs, 1980). In the present study, the effect of vitamin E, a physiological membrane radical scavenger (Witting, 1980), on the renal tubular damage and lipid peroxidation caused by Fe-NTA treatment was examined. 0041-008X/88
$3.00
Copyright 0 1988 by Academic Press. Inc. All rigbts of reproduction in any form reserved.
MATERIALS
AND
METHODS
Animals and Fe-NTA administration. Weanling male Wistar rats (Shizuoka Laboratory Animal Center, Shizuoka) were given standard rat chow (Funahashi-nojo, Chiba) or a synthetic basic diet with or without vitamin E supplement (Oriental Yeast, Tokyo). The basic diet without vitamin E supplement is referred to as a vitamin E-deficient diet, and those containing 20 mg/kg diet of DL-a-tocopheryl acetate and 585 mg/kg diet of DL-a-tocopheryl nicotinate are referred to as a vitamin E-sufficient and vitamin E-supplemented diets, respectively. Rats were given ip injections of Fe-NTA solution which were prepared as previously described (Awai et al., 1979). Some of the rats were given noncomplexed NTA (168 mg/kg body wt, ip), which was considered to be equivalent to the NTA portion of the Fe-NTA dose at 10 mg Fe/kg body wt. The experimental groups, their diets and their Fe-NTA doses are shown in Table 1. Rats were killed by decapitation and the kidneys were quickly excised and processed for histologic study or lipid peroxidation assay. Light microscopy. The tissues were processed routinely and stained with hematoxylin and eosin. The renal cortex, where most of the proximal tubules belong to the pars convoluta, and the medullary outer stripe, where the straight portion of the proximal tubules is dominant, were separately analyzed. The percentage of tubules showing cell fragmentation and karyorrhexis was determined by light microscopy under low-power magnification (X100). Five to ten fields were evaluated in each measurement. Determination of lipid peroxidation. All the reagents were of the highest quality avaiable and obtained from
500