Hydroxylation of debrisoquine using perfused liver isolated from Sprague Dawley and DA rats: comparison with in-vivo results.

The hydroxylation of debrisoquine was investigated in Sprague-Dawley (SD) and Dark-Agouti (DA) rats. Female and male rats were phenotyped in-vivo with debrisoquine six times during their growth. The ratios debrisoquine/4-hydroxydebrisoquine of the female DA rats increased until the 15th week and then decreased; but the values of the metabolic ratios never exceeded 2. Female DA rats cannot be considered as genetically deficient for hydroxylation of debrisoquine in regard to the metabolic ratio, but the percentage of debrisoquine excretion is up to ten fold higher than that in the other strains. Therefore SD and DA rat livers were perfused for 2 h when the clearance of debrisoquine was significantly lower in the female DA group than in the other groups. 4-Hydroxydebrisoquine in the perfusate increased with time, but the amount after 120 min was 12 fold lower in the female DA rat group than in the female SD rat group. The results of the male DA group fell between. This study confirms that female DA rats present a lower debrisoquine 4-hydroxylating capacity than other rats but shows that urinary metabolic ratio is not sufficient to assess the deficiency of debrisoquine hydroxylation.