Dose-related Increased Binding of Nickel to Chromatin Proteins; and Changes to DNA Concentration in the Liver of Guinea Pigs Treated with Nigerian Light Crude Oil

Author： Oruambo Ibiba F. Kachikwu Stephanie Idabor Lauretta

Publisher： MDPI

E-ISSN： 1660-4601|4|3|211-215

ISSN： 1660-4601

Source： International Journal of Environmental Research and Public Health, Vol.4, Iss.3, 2007-09, pp. : 211-215

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Abstract

The alteration in nuclear DNA concentration and the concomitant binding of xenobiotics (alkylating agents, heavy metals, etc.) to chromatin constituents may adversely affect gene structure and/or function, and thus initiate carcinogenesis. Binding of nickel to chromatin DNA has been reported to cause DNA damage (cross-links, single-strand breaks), and although many soluble nickel compounds and complexes have been shown to bind to chromatin, porphyrin-complexed nickel (PCN) in crude oils has not been studied. We have determined the dose-related increases in total and chromatin DNA concentrations, and the differential distribution (binding) of PCN (crude oil nickel-CON) to chromatin constituents in livers of adult male guinea pigs treated with 1.25, 2.50 and 5.0 ml/kg bw Nigerian Bonny light crude oil (BLCO) by intraperitoneal injection. The results showed large BLCO-induced increases in total DNA concentrations of 424%, 632% and 436% at 1.25, 2.50 and 5.0 ml/kg bw BLCO respectively over the untreated controls; while it induced equally large increases in chromatin DNA concentrations of 585% and 200% at 2.50 and 5.0 ml/kg bw respectively. In both cases, maximum increases occurred at 2.50 ml/kg bw BLCO. The distribution of PCN in BLCO between chromatin DNA and chromatin proteins (histones and non-histones) showed that at 2.50 and 5.0 ml/kg bw BLCO, nickel content in chromatin DNA reduced by 25% and 12.5% respectively over the controls; while its content in chromatin proteins also reduced by 26%; but increased by 166% at 2.50 and 5.0 ml/kg bw BLCO, respectively over the untreated controls. However, in intra-chromatin comparison, 38.8% more PCN bound to chromatin DNA than to chromatin proteins at 2.50 ml/kg bw; but at 5.0 ml/kg bw BLCO, 90.4% more PCN bound to chromatin proteins than to chromatin DNA. These results show a greater affinity of PCN in BLCO for chromatin proteins over chromatin DNA which may have played a role in the increased DNA concentrations. Also, the results may add critical information to understanding the reactions of porphyrin-complexed nickel in crude oils with chromatin since this has not been studied before. Furthermore, the probable carcinogenicity of BLCO may be implied.