title: Potentiation of EPN-induced inhibition of liver microsomal carboxylesterase by addition of liver cytosol from 6-aminonicotinamide-treated, starved rats.
abstract: Addition of liver cytosol from 16 hr-starved rats treated with 6-aminonicotinamide to rat liver microsomes caused potentiation of the anti-carboxylesterase action of ethyl-p-nitrophenyl phenylphosphonothioate (EPN). This was not found when liver cytosol from non-pretreated rats after 16 hr-starvation was used. This potentiation of EPN-induced inhibition of carboxylesterase may be, at least in part, explained by the fact that treatment of rats with 6-aminonicotinamide resulted in a significant increase in NADPH level in liver cytosol which, in turn, stimulated formation of an EPN oxygen analog, a potent inhibitor of carboxylesterase, through cytochrome P-450-coupled monooxygenase.
mesh_terms: D015120:6-Aminonicotinamide / Q000494:pharmacology*; D000818:Animals; D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors*; D003600:Cytosol / Q000378:metabolism*; D066298:In Vitro Techniques; D007306:Insecticides / Q000494:pharmacology*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009536:Niacinamide / Q000031:analogs & derivatives*; D004849:Phenylphosphonothioic Acid, 2-Ethyl 2-(4-Nitrophenyl) Ester / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013217:Starvation / Q000378:metabolism
chemical_list: D007306:Insecticides; D009243:NAD; D004849:Phenylphosphonothioic Acid, 2-Ethyl 2-(4-Nitrophenyl) Ester; D009536:Niacinamide; D015120:6-Aminonicotinamide; D009249:NADP; D006899:Mixed Function Oxygenases; D002265:Carboxylic Ester Hydrolases