DRUG-METABOLIZING ENZYME-SYSTEMS IN THE HOUBARA BUSTARD (CHLAMYDOTIS-UNDULATA)

This study compared catalytic and immunochemical properties of drug me tabolizing phase I and II enzyme systems in houbara bustard (Chlamydot is undulata) liver and kidney and rat liver. P450 content in bustard l iver (0.34 +/- 0.03 nmol mg(-1) protein) was 50% lower than that of ra t liver (0.70+/-0.02 nmol mg(-1) protein). With the exception of anili ne hydroxylase activity, monooxygenase activities using aminopyrine, e thoxyresorufin and ethoxycoumarin as substrates were all significantly lower than corresponding rat liver enzymes. As found in mammalian sys tems the P450 activities in the bird liver were higher than in the kid ney. Immunohistochemical analysis of microsomes using antibodies to ra t hepatic P450 demonstrated that bustard liver and kidney express P450 2Cl1 homologous protein; no appreciable cross-reactivity was observed in bustards using antibodies to P4502E1, 1A1 or 1A2 isoenzymes. Glutat hione content and glutathione S-transferase (GST) activity in bustard liver were comparable with those of rat liver. GST activity in the kid ney was 65% lower than the liver. Western blotting of liver and kidney cytosol with human GST isoenzyme-specific antibodies revealed that th e expression of alpha-class of antibodies exceeds mu in the bustard. I n contrast, the pi-class of GST was not detected in the bustard liver. This data demonstrates that hepatic and renal microsomes from the bus tard have multiple forms of phase I and phase II enzymes. The multipli city and tissue specific expression of xenobiotic metabolizing enzymes in bustards may play a significant role in determining the pharmacoki netics of drugs and susceptibility of the birds to various environment al pollutants and toxic insults. (C) 1998 Elsevier Science Inc. All ri ghts reserved.