The biliary excretion of thyroxine and glucuronic acid conjugate in normal and Gunn rats.

Abstract

Eighteen hr after ip injection of 125I-thyroxine (T4) in homozygous Gunn rats, the 125I bile:plasma (B/P) ratios and plasma clearance of T4 into bile were one—third of normal. Paper chromatography revealed a gross deficiency in the amount of T4-glucuronide (T4-G) present in the bile, with a relative excess in the quantities of I∼ and free T4. Normal rats excreted 7.8% of iv injected 131I-T4 into the bile in 200 min compared to only 3.8% in Gunn rats. 125I-T4-G was prepared biosynthetically. Normal rats were injected with 125I-T4, bile was collected and chromatographed on paper and the T4-G region was eluted. The 125I-T4-G was reasonably radiochemically pure as shown by 2-dimensional paper chromatography and by its hydrolysis to free T4 with ²-glucuronidase. Intravenously injected 125I-T4-G was very rapidly excreted into the bile in both normal and Gunn rats. In both initial B/P ratios around 200 were observed and 50% of the dose was excreted in the bile in the first 20 min; virtually all was excreted by 3...