RESUMEN
Avian species contain low levels of enzymes that hydrolyze organophosphorus compounds (OPs), and chickens are used as a model of OPs delayed neurotoxicity. For both reasons, we studied the ability of chicken tissue for OP detoxication. A significant activating effect of Cu2+ on the hydrolysis of O-hexyl O-2,5-dichlorophenyl phosphoramidate (HDCP) was observed in hen plasma and the microsomal fractions of the liver, brain, and mainly in hen serum, by spectrophotometric and chiral chromatography methods. The concentration of 1 mM of Cu2+ or Zn2+ showed 200% and 168% activation, respectively, in hen plasma compared with the Ca2+-dependent hydrolysis, whereas these cations had an inhibitory effect on soluble liver and brain fractions. An increase of 1.5 to 19.5 fold in HDCP hydrolyzing activity was obtained for the 30-250 µM Cu2+ range when using chicken serum instead of hen plasma. This Cu2+-dependent hydrolysis in chicken serum was stereoselective for the R-(+)-HDCP isomer, which proved the opposite to the Ca2+-dependent stereoselective hydrolysis of the S-(-)-HDCP isomer reported in rat and rabbit serum. The level of copper needed to exert this effect should be further evaluated for its suitability for potential therapeutic and biotechnological applications.
