title: Kidney dysfunction and cadmium exposure--factors influencing dose-response relationships.
abstract: Our early toxicological studies showed that metallothionein (MT) is a protein that carries cadmium (Cd) to the kidney, explaining why Cd exposures during long time periods may give rise to kidney dysfunction. This dysfunction is usually considered to be the critical effect, i.e. the adverse effect that occurs at the lowest exposure level. MT also provides intracellular protection against cadmium toxicity. In studies of population groups in cadmium contaminated areas in China, we investigated factors that affected the relationship between internal dose of Cd, as indicated by blood Cd (BCd) or urinary Cd (UCd), and the prevalence of kidney dysfunction. We found dose-response relationships between UCd and the prevalence of increased levels of biomarkers of renal tubular dysfunction (urinary beta-2-microglobulin, B2M, or N-acetyl-beta-d-glucosaminidase - NAG) or urinary albumin (UAlb), a biomarker of glomerular kidney dysfunction. Two years after Cd intake from contaminated rice was diminished, renal tubular dysfunction appeared unchanged or aggravated among those with higher UCd; Another 8 years later, i.e. 10 years after Cd intake was decreased, the prevalence of renal tubular dysfunction was still increased but UAlb had returned to normal. Factors that influenced the dose-response relationships were: (1) time after maximum exposure. (2) Concomitant exposure to other nephrotoxic agents such as inorganic arsenic. (3) Cd induced metallothionein mRNA levels in peripheral blood lymphocytes, used as a biomarker of the ability of each person, to synthesize MT. (4) The occurrence of increased levels in blood plasma of autoantibodies against MT. The two last points further support a role in humans of MT as a protective protein against tissue damage from cadmium and gives support to previous ideas developed partly in experimental systems.
authors.affiliation: Occupational and Environmental Medicine, Department of Public Health and Clinical Medicine, Umea University, SE-90187 Umea, Sweden. gunnar.nordberg@envmed.umu.se
authors.forename: Gunnar
authors.initials: G
authors.lastname: Nordberg
authors.forename: Taiyi
authors.initials: T
authors.lastname: Jin
authors.forename: Xunwei
authors.initials: X
authors.lastname: Wu
authors.forename: Jian
authors.initials: J
authors.lastname: Lu
authors.forename: Liang
authors.initials: L
authors.lastname: Chen
authors.forename: Yihuai
authors.initials: Y
authors.lastname: Liang
authors.forename: Lijian
authors.initials: L
authors.lastname: Lei
authors.forename: Feng
authors.initials: F
authors.lastname: Hong
authors.forename: Ingvar A
authors.initials: IA
authors.lastname: Bergdahl
authors.forename: Monica
authors.initials: M
authors.lastname: Nordberg
mesh_terms: D002104:Cadmium / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism*; D008668:Metallothionein / Q000378:metabolism
chemical_list: D002104:Cadmium; D008668:Metallothionein