OBJECTIVEIn order to explore the pathway of dealkylation of pesticides other than cytochrome P450 monocoxygenases, lipoxygenase (LOX)-mediated demethylation of aminocarb and some other pesticides were measured.

METHODFormaldehyde generated in the reaction was estimated by Nash reaction to express the rate of demethylation of pesticides mediated by soy lipoxygenase (SLO).

RESULTSN-demethylation of aminocarb mediated by SLO was found to depend on the incubation time, concentration of the enzyme, concentration of aminocarb and hydrogen peroxide. Under optimal conditions, Vmax value of 18 nmol of formaldehyde.min-1.nmol-1 of lipoxygenase was observed. The reaction exhibited Km values of 3.4 mmol/L for aminocarb and 235 mumol/L for hydrogen peroxide. A strong inhibition of the reaction by nordihydroguaiaretic acid, gossypol, and phenidone clearly implicated the lipoxygenase involvement as the protein catalyst. A significant decline in the formaldehyde accumulation in the presence of either reduced glutathione or dithiothreitol suggested generation of a free radical species as an initial oxidation intermediate during the demethylation of aminocarb by SLO. The inhibition of formaldehyde generation by butylated hydroxyanisole(BHT) and butylated hydroxy toluene(BHA) further supported this contention. In addition to aminocarb, seven other pesticides were also found to undergo N-demethylation, albeit at relatively low rates.

CONCLUSIONCertain pesticides may oxidatively undergo dealkylation via the lipoxygenase pathway in animals and plants.

Butylated Hydroxyanisole ; pharmacology ; Butylated Hydroxytoluene ; pharmacology ; Dealkylation ; Free Radicals ; Lipoxygenase ; physiology ; Pesticides ; metabolism ; Phenylcarbamates ; metabolism ; Soybeans ; enzymology

Effects of feeding 2(3)-tert-butyl 4-hydroxyanisole (BHA) and 3, 5-di-tert-butyl 4-hydroxytoluene (BHT) on the rates of mixed function oxidation and conjugation enzyme reactions have been determined using isolated hepatic microsomal fractions and isolated perfused livers of mice. The treatments with either of the antioxidants have increased the rates of O-demethylation for p-nitroanisole and of O-deethylation for 7-ethoxycoumarin up to 2-fold, both in microsomes and in perfused liver. Analysis of the perfusate showed that the increased amounts of p-nitrophenol and 7-hydroxycoumarin produced by the elevated mixed-function oxidase activities were reflected by the increase in the amounts of glucuronide conjugates and not in the increase for the amounts of the sulfate ester conjugates. Comparison of results also indicated that in the perfused liver, the maximal rate of metabolite conjugation is limited by the maximal rates of the initial mixed function oxidase activities.
Alkylation ; Animal ; Anisoles/metabolism ; Anisoles/pharmacology* ; Butylated Hydroxyanisole/administration & dosage ; Butylated Hydroxyanisole/pharmacology* ; Butylated Hydroxytoluene/administration & dosage ; Butylated Hydroxytoluene/analogs & derivatives* ; Butylated Hydroxytoluene/pharmacology ; Comparative Study ; Coumarins/metabolism ; Female ; Glucuronosyltransferase/metabolism ; Liver/metabolism* ; Mice ; Microsomes, Liver/enzymology ; Microsomes, Liver/metabolism* ; Mixed Function Oxygenases/metabolism ; Oxidation-Reduction ; Perfusion ; Support, U.S. Gov't, P.H.S.

Butylated hydroxytoluene (BHT) can inhibit experimental atherosclerosis in animals. Although the agent is an antioxidant, the exact mechanism of the reaction in atherosclerosis is still unknown. To investigate the effects of BHT on expression of P-selectin (PADGEM, GMP-140), intercellular adhesion molecule-1 (ICAM-1) and class II MHC (Ia) antigen, we proposed an experiment on rats. Male rats (n=18 per group) were fed either a normal cholesterol control diet, a normal cholesterol diet containing 0.5% BHT (BD), a high cholesterol diet containing 1.5% cholesterol and 0.1% sodium cholate (CD), or the CD diet containing 0.5% BHT (BCD). Rats were sacrificed after 3 days, and after 1, 2, 4, 10, and 17 weeks of dietary treatment. Although there was no gross or light microscopic atherosclerotic lesions, scanning electron microscopy revealed monocytic adhesion to aortic endothelium and mild endothelial injuries in CD and BCD groups. Immunohistochemically, the addition of BHT to a high cholesterol diet inhibited P-selectin expression but not in ICAM-1 and Ia antigen. These findings suggest that in rats, high cholesterol diets induce expression of ICAM-1, P-selectin and Ia antigen. In addition, the antiatherogenic effect of BHT may play a role in the inhibition of P-selectin.
Animal ; Antioxidants/pharmacology ; Antioxidants/metabolism* ; Aorta, Abdominal/ultrastructure ; Aorta, Abdominal/pathology ; Aorta, Thoracic/ultrastructure ; Aorta, Thoracic/pathology ; Butylated Hydroxytoluene/pharmacology ; Butylated Hydroxytoluene/metabolism* ; Cholesterol/metabolism ; Cholesterol, Dietary/metabolism* ; Male ; Microscopy, Electron, Scanning ; P-Selectin/biosynthesis* ; Rats ; Rats, Sprague-Dawley