The effect of signal grass (Brachiaria decumbens) on drug-metabolizing enzymes in sheep and comparison with normal cells

The effect of Brachiaria decumbens (signal grass) on drug-metabolizing enzy mes was studied in sheep. After 14 d of grazing a pure signal grass pasture , significant declines were observed in hepatic aminopyrine N-demethylase a nd aniline 4-hydroxylase (phase I biotransformation) and in conjugative enz ymes UDP-glucuronyltransferase and glutathione S-transferase. Kidney enzyme s were significantly decreased except for UDP-glucuronyltransferase. Enzyme activities were also compared for normal sheep and cattle livers and kidne ys. Lower activities were found in cattle, indicating that factors other th an biotransformation are responsible for the clincial tolerance of cattle t o B decumbens toxicity.