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Abstract
The present work was performed to study the protective effect of melatonin and vitamin C as an antioxidants and free radical scavengers on the oxidative stress and morphological changes induced by hexavalent chromium Cr (VI) administration to male Swiss albino mice. In this study, the LPO levels, CP levels, total peroxide levels, CAT activity, SOD activity and GSH concentration as well as the morphological changes in the liver and kidneys were examined.
The present work included two experiments Experiment I: In this experiment, the mice were divided in to four groups, 20 mice each.
* The first group: (20 mice) was designated Cr (VI), was injected
with chrome at a dose of 20 mg/Kg body weight.
* The second group: (20 mice) was designated Cr (VI) + Melt was
injected subcutaneously with Melatonin at a dose of 10 mg/Kg body weight. The administration of Melatonin was 30 min before Cr (VI) injection and was given at two hours before light out.
* The third group: (20 mice) was designated Cr (VI) + Vit.C was
injected subcutaneously with Vitamin C at a dose of 200 mg/Kg body weight the administration of Vit.C was 30 min before Cr (VI) injection and was given at 4 PM.
* The fourth group: (20 mice) served as control where mice were
injected with vehicles only. All the above injections were repeated daily for 30 days.
Experiment II: In this experiment, the mice (60) were daily injected subcutaneously with chrome at the same dose as experiment I (20 mg/Kg body weight). After 30 days of Cr (VI) administration, the mice were divided into three subgroups.
The first subgroup: (20 mice) was designated (Recov), the animals were left for recovery without any type of treatment for 30 days.
The second subgroup: (20 mice) was designated (Recov + Melt). the animals were given daily subcutaneous injection of Melatonin for recovery at a dose of 10 mg/Kg body weight for 30 days.
The third subgroup: (20 mice) was designated (Recov + Vit.Ci the animals were given daily subcutaneous injection of Vitamin C for recovery at a dose of 200 mg/Kg body weight for 30 days.
The main results obtained from this study are summarized as the following:
Cr (VI) administration greatly stimulated LPO, CP and tota^
peroxide in the liver and the kidneys homogenates versus those of
control animals.
Cr (VI) administration greatly inhibited CAT activity, SOD
activity and GSH concentration in the liver and kidneys
homogenates versus those of control animals.
Melatonin and vitamin C exerted a powerful inhibitory effect c:
the increased levels of LPO, CP and total peroxide in the
examined tissues compared to those subjected to Cr (VI)
administration. • Melatonin and vitamin C exerted a powerful stimulatory effect of
the activities of CAT and SOD as well as restoration to the
concentration of GSH in the examined tissues compared to those
subjected to Cr (VI) administration.
Cr (Vl)-administration markedly induced severe macro
morphological changes in the studied tissues compared with
control animals.
Melatonin and vitamin C proved to have strong protective effect
in the prevention of Cr (Vl)-induced toxicity and malfunctions in
the studied tissues. Cr (Vl)-administration markedly increased the amount of
connective tissue fiber in the hepatic and renal tissues versus to
those of control mice.
Melatonin and vitamin C administration reduced the amount of connective tissue fiber in the studied organs. Cr (Vl)-administration reduced the amount of carbohydrate materials in the liver and the kidneys versus the contents of control animals.
Melatonin and vitamin C administration restored the amount of carbohydrate material in liver and kidneys tissues. Comparison between the recovery of the mice after Cr (VI) administration by lifting the animals without any treatment or giving them melatonin or vitamin C, the results showed that melatonin and vitamin C significantly enhanced the recovery of mice and the studied parameters tend to normal feature.
Upon comparing of the efficiency of melatonin and vitamin C regarding the protection, it was found that in liver and kidneys melatonin was strongly reduced the levels of LPO, CP and total peroxide in Cr (Vl)-exposed mice in experiment I and II more than vitamin C. At the same time, vitamin C exerted more protection than melatonin in total peroxide in experiment 1 and II.
Melatonin was strongly increasing the activity of CAT and concentration of GSH in the liver of Cr (Vl)-exposed mice of experiment I and II compared with vitamin C. Vitamin C exerted more stimulation to SOD activity than did by melatonin in experiment I and II.
Regarding the morphological changes in the liver, comparing between the protective efficiency of melatonin and vitamin C one can realize the following:
Melatonin exerted more protective effect than vitamin C in the morphological structure restoration. Regarding the connective tissue fiber formation, both melatonin and vitamin C exerted nearly the same protective effect. However, the content of carbohydrate materials restoration was strong by vitamin C administration than did by melatonin in experiment 1. In experiment II, both melatonin and vitamin C exerted nearly the same protective effect of the morphological changes induced b;-Cr (VI). Vitamin C exerted more reduction to the amount of connective tissue fibers than melatonin. Regarding the caibotvydratc restoration, melatomrv exerted mote effect than vitamin C.
In the kidney, by comparing the protective effect of melatonin and vitamin C. one can easily detect the stronger effect of melatonin than vitamin C in the improvement of tissue architecture towards normality. Regarding the connective tissue fiber reduction and PAS-reaction positivity, melatonin exerted highly protective effect more than vitamin C in experiments I and II.
h could be concluded that the protective role of melatonin and vit.C against Cr (VI) toxicity is clear in experiment I (prevention) and experiment II (treatment). However, the preventive role of melatonin and vit.C against toxicity of Cr (VI) in experiment I was more potent and more powerful! than that of experiment II (treatment).