Effect of Nicotinic Acid on Pool Size and Turnover of Taurocholic Acid in Normal and Hypothyroid Dogs. ∗

Summary

The rate of disappearance of taurocholic-¹⁴C acid from bile was studied in a group of dogs after oral administration of cholic-carboxyl-¹⁴C acid. The specific activity of taurocholic acid was determined in multiple small samples of bile by quantitative thin-layer chromatography and liquid scintillation counting; biologic half-life, pool size, and turnover of taurocholic acid were calculated. Hypothyroidism, induced in 2 dogs by administration of ¹³¹I and propylthiouracil, increased the plasma cholesterol concentration and resulted in a prolonged half-life, an increased pool size, and an increased turnover of taurocholic acid. Nicotinic acid did not alter the dynamics of the metabolism of taurocholic acid in either the normal or the hypothyroid dogs, despite its marked hypo-cholesterolemic effect in the hypothyroid dog.