Accelerated Biliary Thyroxine Secretion in Rats Treated with 3-Methylcholanthrene 1

Summary

Rats received a single dose of 10 mg of 3-methylcholanthrene (MCA). Twenty-four hours later each rat received a 0.5 μCi of ¹³¹I-labeled L-thyroxine (¹³¹I-T₄). Bile was collected in hourly samples for 4 hr following ¹³¹I-T₄. Average total (4 hr) biliary secretion of ¹³¹I by MCA-treated rats was approximately twice that in control rats. Average volume flow rate of bile was not significantly different in the two groups. During the first hour of bile collection, biliary clearance of plasma ¹³¹I in MCA-treated rats was more than 3 times that in control rats. The major fraction of biliary ¹³¹I in both groups appeared to be T₄-glucuronide.