Immediate and dose-response related increase of biliary excretion of reverse triiodothyronine after propylthiouracil administration.
In a group of rats infused with L-thyroxine (0.13 micrograms T4 in 0.6 ml alkaline saline per hour) for 6 h to which an infusion of propylthiouracil (PTU) was added beginning from the 3rd hour (2 mg PTU in 0.6 ml saline per hour) a significant increase of biliary excretion of reverse triiodothyronine (rT3) was found. In another experiment a dose-response related rT3 excretion by bile was observed in groups of rats infused with 0.05, 0.10, 0.20 or 0.40 mg PTU in 1.2 ml alkaline saline per 2 h, all animals receiving a pulse dose of 1 micrograms rT3 at the beginning of PTU infusion. It was concluded that the increase of rT3 excretion results from the inhibition of 5'-deiodinase type I activity in the liver caused by PTU. It thus appears that such phenomenon may be used as in vivo marker of that enzyme activity.
Langer
P
P
Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava.
Gschwendtová
K
K
D000818:Animals; D001646:Bile / Q000737:chemistry / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D007262:Infusions, Intravenous; D008297:Male; D011441:Propylthiouracil / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013970:Thyronines / Q000008:administration & dosage / Q000494:pharmacology; D013997:Time Factors; D014285:Triiodothyronine, Reverse / Q000032:analysis / Q000378:metabolism*
D013970:Thyronines; D014285:Triiodothyronine, Reverse; D011441:Propylthiouracil