الفهرس 
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Abstract
Cadmium chloride is one of the cadmium salts which has bad effects on the genetic material of living organisms. This work was done to study the genotoxic effects of cadmium chloride on the chromosomes and DNA of male mice and the possible protective effect of zinc chloride against cadmium chloride toxicity. This study was done in two experiments as follows: 1st Experiments (Acute exposure to cadmium chloride): In this experiment, different doses of cadmium chloride were injected intrapritoneally into mice to study the acute effects. 36 mice were used and were divided into 6 groups as follows: The first group was kept as a control group (without any treatment). The second group was given zinc chloride in drinking water 70 mg∕kg b.wt. The third group was injected intraperitoneally with Cdcl2 at a dose of 10 mg∕kg b.wt. This is equal to 1∕10 LD50 of cadmium chloride. The fourth group was injected intraperitoneally with 10 mg∕kg b.wt of cadmium chloride in addition to 70 mg∕kg b.wt of zinc chloride in drinking water. The fifth group was injected intraperitoneally with Cdcl2 at a dose of 20 mg∕kg b.wt. This is equal to 1∕5 LD50 of cadmium chloride. The six group was injected intraperitoneally with Cdcl2 at a dose of 20 mg∕kg b.wt of cadmium chloride in addition to 70 mg∕kg b.wt of zinc chloride in drinking water. A half of the animals in each group was sacrificed after 24 hrs. The other half was sacrificed after 48 hrs from the beginning of the administration. ΙΙ- 2nd Experiment (Chronic exposure to cadmium chloride): In this experiment, 40 mice were used and were divided into four groups as follows: The first group was kept as a control group (without any treatment). The second group was given zinc chloride orally (in diet) at a dose of 70 mg∕kg b.wt. The third group was given cadmium chloride orally (in diet) at a dose of 5 mg∕kg b.wt. This dose is equal to 1∕20 mg ∕kg b.wt. The fourth group was given 5 mg∕kg b.wt of cadmium chloride in diet in addition to 70 mg∕kg b.wt of zinc chloride in drinking water. All animals were sacrificed and samples were collected after 3 months from the beginning of the administration. from the current study, the following results were obtained: Acute treatment: The acute treatment of cadmium chloride induced a significant effect (P >0.05) on the chromosomal aberrations at a dose of 1∕10 and1∕5 LD50 for the two periods of treatment (24 and 48 hrs). Means of aberrant cells at 1∕10 LD50 of Cdcl2 and 1∕5 LD50 of Cdcl2 for 24 hrs were high and represented 32.00 ± 1.40 and 36.00 ± 0.50. But they represented 16.60 ± 0.88 to the control and 18.00 ± 0.57 to the Zncl2 treated group. Means of aberrant cells at 1∕10 LD50 and 1∕5 LD50 for 48 hrs were also high and represented 34.00 ± 0.33 and 37.33 ± 0.59 but they represented 17.00 ± 0.33 to the control and 18.66 ± 0.88 to the Zncl2 treated group. It was found that the different types of chromosomal aberrations at 24, 48 hrs were chromatid deletion, end to end association, centromeric attenuation, centric fusion, chromatid break, chromatid gap, fragment, ring chromosome, polyploidy and hypopliody. Administration of zinc chloride in drinking water at a dose of 70 mg∕kg b.wt before the acute exposure to cadmium chloride induced a decrease in the number of aberrant cells. The means of aberrant cells at 1∕10 LD50 of cadmium chloride and1∕5 LD50 of cadmium chloride at 24 hrs were 32.00 ±1.40 and 36.00 ± 0.50 while they decreased in the 1∕10 LD50 of cadmium chloride + zinc chloride and 1∕5 LD50 of cadmium chloride + zinc chloride to 29.00 ± 1.20 and 33.00 ± 0.88. Also at 48 hrs the means of aberrant cells at 1∕10 LD50 of cadmium chloride and 1∕5 LD50 of cadmium chloride were 34.00 ± 0.33 and 37.33 ± 0.59 and they decreased in 1∕10 LD50 of cadmium chloride + zinc chloride and 1∕5 LD50 of cadmium chloride + zinc chloride to 29.33 ± 0.66 and 33.57 ± 0.16. Chi square analysis revealed that there was a significant difference in the rate of mitotic index at 24 and 48 hrs between control and treated groups. This indicated that acute administration of cadmium chloride decreased the rate of cell division (mitotic index) of mice bone marrow cells at 24 and 48 hrs exposure. ΙΙ- chronic treatment: The chronic treatment with cadmium chloride for 3 months induced a significant effect (P >0.05) on chromosomal aberrations at a dose level of 1∕20 LD50. Means of aberrant cells at 1∕20 LD50 for three months were high and represented 34.60 ± 0.97. But they represented 13.20 ± 1.15 to the negative control group and 19.60 ± 0.97 to the Zncl2 treated group. chronic exposure to cadmium chloride increased chromosomal aberrations in the form of chromatid deletion, end to end association, centromeric attenuation, centric fusion, chromatid break chromatid gap, polyploidy and hypopliody. While treatment with zinc chloride in addition to cadmium chloride decreased the rate of chromosomal aberrations. Administration of zinc chloride at a dose of 70 mg∕kg b.wt decreased the number of aberrant cells as the means of aberrant cells at 1∕20 LD50 of cadmium chloride were 34.60 ± 0.97 and they were significantly decreased to 28.20 ± 1.90 in 1∕20 LD50 of cadmium chloride + zinc chloride. Chi square analysis revealed that there was a significant difference between the control and treated groups in the rates of mitotic division at 3 months. ΙΙΙ- 3rd Experiment (Random amplified polymorphic DNA- polymerase Chain Reaction) (RAPD-PCR): In this study RAPD-PCR was performed using 10 random primers and the results were as follows: primers only amplified DNA but the other 5 primers failed to amplify DNA. Primer 1 (OPA1) whos sequence was 5`- CAGGCCCTTC-3` was useful in identifying control group and Zncl2 treated one. Primer 2 (OPA6) whose sequence was 5`- GGTCCCTGAC-3` was a good marker for identifying the control group. Primer 3 (OPA9) whose sequence was 5`-GGGTAACGCC-3` was a good indicator for Zncl2 treated group. Primer 4 (OPC2) whose sequence was 5`- GTGAGGCGTC-3` was useful for identifying Cdcl2 treated group and Zncl2 treated one. Primer 5 (OPC8) whose sequence was `5- TGGACCGGTG-3` was a good marker for identifying the control group. Conclusion: from the results of this study, it could be concluded that: Cadmium chloride had a genotoxic on mice and produced a significant increase in chromosomal aberations in both the acute and chronic treatments. Cadmium chloride significantly reduced the rate of cell division (mitotic index) in acute and chronic treatments. Cadmium chloride produced DNA damage after chronic exposure as was revealed by RAPD-PCR. The use of zinc chloride protected against cadmium chloride genotoxicity as it significantly decreased the frequency of chromosomal aberrations and DNA damage.