Study On The Hprt Locus Mutation Induced By Cadmium Chloride, Corresponding Mechanisms And The Effects Of Zinc Chloride As An Inhibitor

Objective: Cadmium is a ubiquitous environmental contaminant that has been evaluated as an assured human carcinogen. The main sources of cadmium exposure in human are tobacco smoke, food and industrial pollution. Cadmium has a long biological half-life of more than 25 years which makes it a cumulative toxin. Unfortunately, there's no available treatment for chronic cadmium poisoning. Mutation has been regarding as crucial to the initiating and promoting stages of carcinogenesis. In the present study, we determine the mutagenicity of cadmium comprehensively, searching the corresponding mechanisms and the effects of zinc as an inhibitor in vitro. The aim of this study is to explore the basic mechanisms of carcinogenesis of cadmium and to provide experimental data for the future steps carried out to prevent the exposed population from the carcino-genicity of cadmium.Methods: An in vitro system with the Chinese hamster lung fibroblast cell,V79-an international accredited cell line, was taken in the present study, which contained four parts. The acute and chronic cytotoxicity of Cadmium chloride (CdCl2)on V79 cells, offering the bases for dosage in the latter parts; the change of hprt locus mutation frequency in V79 cells exposed to a wide range doses of CdCl2 DNA damage, effects on the process of DNA repair and apoptosis were further carried out in V79 cells treated with different concentrations of cadium by Alkli single cell gel electrophoresis (SCGE) , the apoptosis effects were also assessed by Ardine orange/ethidum bromide double fluorescent dyestaining combined with the Confocal Scanning Laser Microscope(CSLM). The inhibitive effects by physiological concentration of zinc chloride (ZnCl2) were investigated by combined treatment with 10mol/L ZnCl2 and various concentrations of cadmium simultaneously on V79 cells in the above three parts. In the last part, the mass spectrography and the fluorescent probe of ROS(DCFH-DA) combined with CSLM were used to find the intracellular Cd2+ and Zn2+ ions and ROS respectively after treatment of CdCl2 alone or with physiological concentration of ZnCl2 simultaneously to explore the direct and indirect mechanisms of cadmium toxicity and the ways of the inhibitive effects for inorganic zinc.Conclusion: CdCl2 can cause the acute and chronic cytotoxicity in V79 cells. The mutation frequency of hprt increases in V79 cells exposed to CdCl2 with two peak values could be detected, which hasn't been reported by other researchers. The inducement of CdCl2 on hprt locus mutation can be attributed to the effects of CdCl2 on DNA break, the process of DNA repair and apoptosis, in which the facilitation of DNA break, inhibition of DNA repair process may be the main causes. Physilogical concentration of ZnCl2 can virtually inhibit all the above-mentioned effects of CdCb, the impact of ZnCl2 on hprt mutation caused by CdCl2 also hasn't been published until now.The inhibitive effects of zinc may be due to the decrease of intracellular Cd2+ and ROS caused by zinc, so maintaining the normal level of humoral zinc may facilitate the protection from carcinogenesis of cadmium. It can also be concluded that SCGE is a rapid,economic and way to detect DNA damage, DNA repair process and apoptosis induced by the environmental toxins, while CSLM has the advantages in qualitative and quantitative analyses of the image-based biological and pathological effects.