In Vivo Study of Iodothyronine Deiodination in Rat Liver: Effect of Salicylate on Biliary Excretion of Several Iodothyronines

Summary

Biliary excretion of total (i.e. conjugated plus uneonjugated) thyroxine (T₄), 3,5,3′-triiodothyronine (T₃), 3,3′,5′-triiodothyronine (rT₃), 3,5-diiodothyronine (3,5-T₂), 3,3′-diiodothyronine (3,3′-T₂) and 3′,5′-diiodothyronine (3′,5′-T₂) was measured with the aid of specific radioimmunoassay in 17 control rats and in 31 rats injected sodium salicylate i.v. (200 mg kg^-1). The animals were anesthetized with pentobarbiturate and the samples of bile were taken in subsequent 2 h periods from a drained bile duct. In controls a gradual decrease of excretion of all compounds measured was found during 10 h observation period. In contrast, after salicylate injection a transient increase of total bile volume and of T₄, T₃ and 3,5-T₂ excretion was observed followed by a remarkable decrease, while a multifold and prolonged increase of the excretion of rT₃,3,3′-T₂ and 3′,5′-T₂ was found. These data suggest an acute and remarkable effect of salicylate on T₄ deiodinating pathway in the liver.

Key-Words:

Salicylate - Thyroid Hormone Metabolism - Iodothyronines - Liver - Bile