title: The herbicide dicamba (2-methoxy-3,6-dichlorobenzoic acid) is a peroxisome proliferator in rats.
abstract: The widely used broad leaf herbicide, dicamba, or Banvel, is similar in structure to xenobiotics which induce hepatic drug metabolism or proliferation of hepatic peroxisomes in rodents. The ability of xenobiotics to effect these hepatic changes often portends their positive outcomes in chronic bioassays. Dicamba's ability to induce hepatomegaly and peroxisome proliferation was studied in male and female Sprague-Dawley rats. Rats were placed on feed containing 0, 0.001, 0.01, 0.1, or 1% dicamba or 0.01% ciprofibrate for 3 weeks. Dicamba had no effect on relative liver weights or feed efficiency in either female or male rats at all doses tested. Dicamba, however, caused a statistically significant increase in peroxisomal beta-oxidation activity in liver homogenates from rats of both sexes fed 1% dicamba. Fatty acyl CoA-oxidase activity was increased in male rats fed 1% dicamba. A protein of M(r) 80 kDa was visible when liver homogenates of female or male rats fed 1% dicamba were subjected to SDS-PAGE. Lauric acid hydroxylase activity and CYP4A-reactive protein were increased in microsomes from male rats fed the highest level of dicamba. Moreover, dicamba was observed to transcriptionally upregulate the peroxisome proliferator-activated receptor (PPAR), a peroxisome proliferator sensitive receptor previously shown to be linked to the transcriptional regulation of a variety of peroxisome-specific enzymes. These studies show that dicamba is a peroxisome proliferator in rats. Although dicamba was not an efficacious inducer of peroxisomal enzymes in these rats, dicamba's ability to transcriptionally activate the PPAR and induce peroxisomal and related enzymes must be considered in the safety evaluation of this herbicide.
authors.affiliation: Department of Nutrition and Food Science, University of Kentucky, Lexington 40506-0054, USA.
authors.forename: P
authors.initials: P
authors.lastname: Espandiari
authors.forename: V A
authors.initials: VA
authors.lastname: Thomas
authors.forename: H P
authors.initials: HP
authors.lastname: Glauert
authors.forename: M
authors.initials: M
authors.lastname: O'Brien
authors.forename: D
authors.initials: D
authors.lastname: Noonan
authors.forename: L W
authors.initials: LW
authors.lastname: Robertson
mesh_terms: D042962:Acyl-CoA Oxidase; D000818:Animals; D001483:Base Sequence; D001835:Body Weight / Q000187:drug effects; D002995:Clofibric Acid / Q000031:analogs & derivatives / Q000378:metabolism / Q000633:toxicity; D042926:Cytochrome P-450 CYP4A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003996:Dicamba / Q000378:metabolism / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005260:Female; D058607:Fibric Acids; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008830:Microbodies / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000378:metabolism; D008969:Molecular Sequence Data; D009929:Organ Size / Q000187:drug effects; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D058607:Fibric Acids; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D002995:Clofibric Acid; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; D042926:Cytochrome P-450 CYP4A; D042962:Acyl-CoA Oxidase; C019304:ciprofibrate; D003996:Dicamba