Absorption, distribution, metabolism and excretion of daily oral doses of [14C]methyl parathion in hens.


Journal Article

Adult hens were given oral daily doses of 2 mg (2 microC(i))/kg/day (14% of oral LD(50) in male rats) of [14C]methyl parathion (O,O-dimethyl O-4-nitrophenyl phosphorothioate) for 10 consecutive days. Five treated hens were sacrificed at 1, 2, 4, 8, 12, 24, and 48 h after the last dose. Methyl parathion was absorbed from the gastrointestinal tract and distributed rapidly. Maximum radioactivity was detected in tissues within 8 h of dosing, (ng methyl parathion equivalent/g fresh tissue or ml plasma): Plasma (189.2), liver (94.7), kidney (146.2), brain (61.4), gastrointestinal tissues (106.7). Methyl parathion was detected in the plasma, kidney and liver, while methyl parathion metabolite p-nitrophenol was detected in the liver and in the kidney. Elimination of methyl parathion from plasma was monophasic with a terminal half-life of 17.5 h, corresponding to an elimination rate constant of 0.039 ng/hr. Most of the absorbed radioactivity was excreted in the combined fecal-urine excreta (98%). Analysis of the metabolites in the excreta revealed that non-conjugated metabolites accounted for 13% of the total excretion. Conjugated metabolites accounted for 87% of the total excretion; of that, 6% as p-nitrophenyl-glucoronide conjugate, 7% as p-nitrophenyl-sulfate conjugate, 23% as bound hot sulfuric acid hydrolyzable residues, and 51% as water soluble metabolites. The presence of majority of radioactivity in the excreta as conjugated metabolites indicates that determining only unbound p-nitrophenol as a biological marker for methyl parathion exposure underestimates total fecal-urine excretion of p-nitrophenol. The slow elimination rate of methyl parathion is significant, since hens are more comparable to humans with respect to their cytochrome P450 activities.

Full Text

Duke Authors

Cited Authors

  • Abu-Qare, AW; Abdel-Rahman, AA; Ahmad, H; Kishk, AM; Abou-Donia, MB

Published Date

  • December 15, 2001

Published In

Volume / Issue

  • 125 / 1-3

Start / End Page

  • 1 - 10

PubMed ID

  • 11701217

Pubmed Central ID

  • 11701217

International Standard Serial Number (ISSN)

  • 0378-4274

Digital Object Identifier (DOI)

  • 10.1016/s0378-4274(01)00409-x


  • eng

Conference Location

  • Netherlands