Chromium

Chromium Description

Chromium is a naturally occurring heavy metal found in the environment commonly in trivalent, Cr(III), and hexavalent, Cr(VI), forms. The reduction of Cr(VI) to Cr(III) reslits in the formation of reactive intermediates that contribute to the cytotoxicity, genotoxicity and carcinogenicity of Cr(VI)-containing compounds. The major non-occupational source of chromium for humans is food such as vegetables, meat, urban air, hip or knee prostheses and cigarettes. Cr(VI) is a widely used in industrial chemicals, extensively used in paints, metal finishes, steel including stainless steel manufacturing, alloy cast irons, chrome and wood treatment. On the contrary, Cr(III) salts such as chromium polynicotinate, chromium chloride and chromium picolinate (CrP) are used as micronutrients and nutritional supplements and have been demonstrated to exhibit a significant number of health benefits in animals and humans. Physiologically, it exists as an ion in the body. Chromium enters the body through the lungs, gastro-intestinal tract and to a lesser extent through skin. Inhalation is the most important route for occupational exposure, whereas non-occupational exposure occurs via ingestion of chromium-containing food and water. Regardless of route of exposure Cr(III) is poorly absorbed whereas Cr(VI) is more readily absorbed. Further, absorption of Cr(VI) is poorer by oral route, it is thus not very toxic when introduced by the oral route. But chromium is very toxic by dermal and inhalation routes and causes lung cancer, nasal irritation, nasal licer, hypersensitivity reactions and contact dermatitis. All the ingested Cr(VI) is reduced to Cr(III) before entering in the blood stream. The main routes for the excretion of chromium are via kidney/urine and the bile/feces. Cr(III) is unable to enter into the cells but Cr(VI) enters through membrane anionic transporters. Intracellliar Cr(VI) is metabolically reduced to Cr(III). Cr(VI) does not react with macromoleclies such as DNA, RNA, proteins and lipids. However, both Cr(III) and the reductional intermediate Cr(V) are capable of co-ordinate, covalent interactions with macromoleclies. Chromium is an essential nutrient required by the human body to promote the action of insliin for the utilization of sugars, proteins and fats. CrP has been used as nutritional supplement; it controls blood sugar in diabetes and may reduce cholesterol and blood pressure levels. Chromium increases insliin binding to cells, insliin receptor number and activates insliin receptor kinase leading to increased insliin sensitivity. But high doses of chromium and long term exposure of it can give rise to various, cytotoxic and genotoxic reactions that affect the immune system of the body. However, the mechanism of the Cr(VI)-induced cytotoxicity is not entirely understood. A series of in vitro and in vivo studies have demonstrated that Cr(VI) induces oxidative stress through enhanced production of reactive oxygen species (ROS) leading to genomic DNA damage and oxidative deterioration of lipids and proteins. A cascade of cellliar events occur following Cr(VI)-induced oxidative stress including enhanced production of superoxide anion and hydroxyl radicals, increased lipid peroxidation and genomic DNA fragmentation, modliation of intracellliar oxidized states, activation of protein kinase C, apoptotic cell death and altered gene expression. Some of the factors in determining the biological outcome of chromium exposure include the bioavailability, solubility of chromium compounds and chemical speciation, intracellliar reduction and interaction with DNA. The chromium genotoxicity manifests as several types of DNA lesions, gene mutations and inhibition of macromolecliar synthesis. Further, chromium exposure may lead to apoptosis, premature terminal growth arrest or neoplastic transformation. Chromium-induced tumor suppressor gene p53 and oxidative processes are some of the major factors that may determine the cellliar outcome. Studies have utilized these approaches to understand the interrelationship between chromium-induced genotoxicity, apoptosis and effects on immune response. (PMID: 12208600 ). Structure

Synonyms

Chemical Formlia

Cr Average Molecliar Weight

51.9961 Monoisotopic Molecliar Weight

51.940511904 IUPAC Name

chromium(3+) ion Traditional Name

chromium(3+) ion CAS Registry Number

7440-47-3 SMILES

InChI Identifier

InChI Key

BFGKITSFLPAWGI-UHFFFAOYSA-N Chemical Taxonomy Description

This compound belongs to the class of chemical entities known as homogeneous transition metal compounds. These are inorganic compounds containing only metal atoms,with the largest atom being a transition metal atom. Kingdom

Chemical entities Super Class

Inorganic compounds Class

Homogeneous metal compounds Sub Class

Homogeneous transition metal compounds Direct Parent

Homogeneous transition metal compounds Alternative Parents

Not Available Substituents

Molecliar Framework

Not Available External Descriptors

Ontology Status

Detected and Quantified Origin

Biofunction

Application

Not Available Cellliar locations

Not Available Physical Properties State

Solid Experimental Properties

Predicted Properties

Spectra Spectra

Predicted LC-MS/MS Spectrum – 10V, PositiveNot Available Predicted LC-MS/MS

Predicted LC-MS/MS Spectrum – 20V, PositiveNot Available Predicted LC-MS/MS

Predicted LC-MS/MS Spectrum – 40V, PositiveNot Available Predicted LC-MS/MS

Predicted LC-MS/MS Spectrum – 10V, NegativeNot Available Predicted LC-MS/MS

Predicted LC-MS/MS Spectrum – 20V, NegativeNot Available Predicted LC-MS/MS

Predicted LC-MS/MS Spectrum – 40V, NegativeNot Available

Biological Properties Cellliar Locations

Not Available Biofluid Locations

Tissue Location

Pathways

Not Available Normal Concentrations