Accumulation and biological effects of metals in wild rats in mining areas of Zambia
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The lead–zinc (Pb–Zn) mine in Kabwe City and the copper–cobalt (Cu–Co) mine in the Copperbelt Province are major mining areas in Zambia. To examine the effects of metal pollution on wildlife, wild black rats (Rattus rattus and Rattus tanezumi) were captured in Kabwe and Chingola (in the Copperbelt Province), and in Lusaka (a noncontaminated site). Wild black rats in Kabwe accumulated significantly higher concentrations of Pb and Cd in various organs than rats from Lusaka. In Chingola, significantly higher concentrations of Cu, Co, Pb, and Cd were accumulated in wild black rats than in rats from Lusaka. These results were in accordance with metal accumulation patterns in soil. From toxicological aspects, concentrations of Pb and Cd in rats were generally low. However, metallothionein-1 (MT-1) and metallothionein-2 (MT-2) mRNA expression levels in wild black rats from Kabwe were significantly higher than those in rats from Lusaka. A generalized linear model (GLM) showed that concentrations of Zn and Cu had positive effects on the MT-1 and MT-2 mRNA expression. These results suggest that wild black rats in Zambian mining sites were exposed to metals that accumulated in their organs, causing biological responses such as MT mRNA induction. GLM indicated that heme oxygenase-1 (HO-1) mRNA expression could be a marker for Cr exposure.
KeywordsMetal Metallothionein Hemeoxygenase Biological responses Generalized linear model Wild rat
This study was supported, in part, by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan awarded to M. Ishizuka (No. 24405004) and Y. Ikenaka (No. 23710038) and foundations of JSPS AA Science Platform Program, Sumitomo, Heiwa Nakajima, and Mitsui & Co., Ltd. One of the authors (S. Nakayama) is a Research Fellow of the Japan Society for the Promotion of Science (No. 2403000402). We would like to acknowledge the financial supports by The Naito Foundation and Sompo Japan Environment Foundation. We gratefully acknowledge the assistance of Dr. Nakozi Kabeta, Provincial Veterinary Officer in Kabwe.
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