title: Changes in leucine transport activity in Chironomus riparius larvae after short-term exposure to potassium dichromate and fenitrothion.
abstract: The effect of sublethal concentrations of potassium dichromate and fenitrothion on sodium-leucine cotransport in brush border membrane vesicles from Chironomus riparius larvae has been investigated. Exposure to potassium dichromate and fenitrothion caused a dose- and time-dependent inhibition of leucine uptake. Transport inhibition is easily detectable at doses 100-fold lower than LD50. Kinetic experiments showed that inhibition was mainly caused by a decrease of the Vmax (680 +/- 53 vs. 382 +/- 23 and 555 +/- 27 nmol/15s/mg protein in control and exposed larvae to K2Cr2O7 and fenitrothion, respectively). Inhibition is possibly related to a variation of sodium ions permeability as evidenced by increased membrane lipid peroxidation. Appropriate control experiments ruled out that the observed differences could be due to changes in general features of membrane preparations. Transport inhibition observed in larvae exposed to potassium dichromate was accompanied by changes in ascorbate peroxidase and dehydroascorbate reductase activities, whereas those exposed to fenitrothion displayed an increase in transaminase activity. The possible value of leucine uptake as biochemical biomarker is briefly discussed. Arch. Insect Biochem. Physiol. 55:90-101, 2004.
authors.affiliation: Dipartimento di Scienze dell'Ambiente e del Territorio, Università di Milano-Bicocca, Milano, Italy.
authors.forename: Matilde
authors.initials: M
authors.lastname: Forcella
authors.forename: Elisa
authors.initials: E
authors.lastname: Berra
authors.forename: Roberto
authors.initials: R
authors.lastname: Giacchini
authors.forename: Giorgio M
authors.initials: GM
authors.lastname: Hanozet
authors.forename: Paolo
authors.initials: P
authors.lastname: Parenti
mesh_terms: D026905:Amino Acid Transport Systems / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002683:Chironomidae / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005278:Fenitrothion / Q000494:pharmacology*; D007700:Kinetics; D007814:Larva / Q000187:drug effects / Q000378:metabolism; D007930:Leucine / Q000031:analogs & derivatives / Q000378:metabolism*; D007931:Leucyl Aminopeptidase / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology; D009994:Osmolar Concentration; D011192:Potassium Dichromate / Q000494:pharmacology*; D014316:Tritium
chemical_list: D026905:Amino Acid Transport Systems; D014316:Tritium; D007931:Leucyl Aminopeptidase; D007930:Leucine; D011192:Potassium Dichromate; D005278:Fenitrothion