الفهرس 
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Abstract
The effects of a chronic vitamin A (retinol palmitate) supplementation at ordinary, double, toxic doses (2500, 5000, or 10000 IU/kg/day) for 60 days on the erythrocytes antioxidant enzymes and redox state parameters including reduced glutathione, glucose -6- phosphate dehydrogenase, glutathione peroxidase, glutathione reductase, superoxide dismutase and catalase activities, hepatic and serum retinol, serum nitric oxide, and electrophoresis pattern of serum proteins were investigated in male Sprague-Dawely rats.
This study was carried out on eighty male Sprague-Dawely rats, 3-6 weeks old, and weighted weighting 120-150 grams. Rats were housed in separate metal cages, fresh and clean drinking water was supplied adlibtium. Rats were kept at a constant environmental and nutritional condition throughout the period of experiment.
Design of experimental work:
Rats under study were randomly divided into four main equal groups, 20 rats each, placed in individual cages and classified as follows:
Group I (Control group): Rats received no treatment and was served as control for all experimental groups.
Group II (Ordinary doses administered group): Rats administered with vitamin A orally and daily at a dose level of 2500 IU/kg body weight /day for 60 days.
Group III (Double doses administered group): Rats administered vitamin A orally in a daily dose of 5000 IU/kg body weight for 60 days.
Group IV (Toxic doses administered group): Rats administered vitamin A orally at a dose level of 10000 IU/kg body weight /day for 60 days.
N.B: During the experimental period, the dosage was adjusted every week according to any change in body weight to maintain similar dose per kg body weight of rat over the entire period of study for each group.
Sampling:
Random blood samples and liver tissue specimens were collected from all animal groups (control and experimental groups) 4 times along the duration of experiment at two, four, six and eight weeks from the onset of treatment with vitamin A.
I- Blood samples:
Blood samples were collected after overnight fasting from the retro-orbital venous plexus located at the medial canthus of the eye using heparinized capillary tubes. Approximately 2 ml of blood samples were collected in screw capped tubes containing heparin anticoagulant solution (20 IU Heparin/1 ml blood). Plasma was separated by centrifugation at 3500 r.p.m. for 10 minutes. After plasma separation, erythrocytes were washed for preparation of erythrocyte lysate.
Preparation of erythrocyte lysate:
Erythrocytes were separated from blood plasma by centrifugation at 3500 rpm for 10 minutes, and then washed three times with a cold isotonic saline solution(0.9%NaCl).The supernatant and the buffy coat were carefully removed after each wash. The red cell pellets were lysed by adding 4 volumes of cold deionized water, and kept in a deep freeze
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at -20°C until used for determination of the following biochemical parameters:
1. Reduced glutathione (GSH).
2. Super oxide dismutase (SOD).
3. Catalase (CAT).
4. Glutathione peroxidase (GPx).
5. Glutathione reductase (GR).
6. Glucose-6-phosphate dehydrogenase (G6PD).
7. Haemoglobin (Hb).
The rest of blood samples were collected in clean dry screw-capped tubes, then allowed to coagulate at room temperature for 30 minutes, and centrifuged at 4000 r.p.m for 10 minutes. The clean, clear-serum was separated by Pasteur pipette and received in dry sterile sample tube, then kept in a deep freeze at -20° C until used for subsequent biochemical analysis. All sera samples were analyzed for the following parameters:
1. Nitric oxide (NO).
2. Retinol.
3. Protein electrophoresis.
4. Total protein.
5. Albumin.
2- Tissue samples (liver):
Liver specimen were taken four times from each group of rats after had been sacrificed by decapitation. Liver rapidly excised and removed from each rats of both control and experimental groups and washed with cold
saline solution (0.9% NaCl) and kept at – 20 0C until used for Retinol analysis.