Correlation between various ratios of serum thyroid hormones and liver cytochrome P-450 in CCl4-treated and untreated rats.

In a search for clinically useful indices of liver microsomal function, the correlation between various ratios of serum thyroid hormones, triiodothyronine (T3) and reverse T3 (rT3), and liver microsomal P-450 was investigated in CCl4-treated and untreated rats. Serum and liver samples were obtained before (untreated group, n = 15) and 4 hr after CCl4 administrations (0.2 ml/kg, s.c.). The CCl4-treated group (n = 11) included five randomly chosen untreated rats. In both groups, the ratios of T3/rT3, rT3/T3, and T3/T3+rT3 correlated significantly with liver cytochrome P-450 levels. From these results, it is suggested that the ratios of T3/T3+rT3, T3/rT3, and rT3/T3 can be used as the indices of liver microsomal P-450 levels and that thyroid hormone metabolism is related to liver cytochrome P-450, as was evidenced in untreated animals.