Effect of adrenaline on biliary excretion of triiodothyronines in rats mediated by alpha1-adrenoceptors and related to the inhibition of 5’-monodeiodination in liver

摘要: Biliary excretion of thyroxine (T4), 3,5,3’-triiodothyronine (T3), 3,3,5’-triiodothyronine (rT3) and diiodothyronines (3, 3’-T2, 3, 5-T2 3’, 5’-T2) was estimated with the aid radioimmunoassay in 3–4 subsequent 2-h samples bile obtained from pentobarbital anesthetized rats through tubing inserted duct. The T3 significantly decreased during 4-h infusion 2400 ng/kg/min adrenaline normal or 6-h latter dose animals preinjected 2 µg T4. Moreover, rT3 increased after 1200 adrenaline. Such increase prevented by a single 10 mg/kg phentolamine (alpha1–2-antagonist) that also 2.5 prazosin (alpha1-antagonist) injected at beginning infusion, but not 6 yohimbine (alpha2-antagonist) every 60 min infusion. In addition, found alpha1-agonist methoxamine (1.5 mg/kg/4 h), while no such effect alpha2-agonist azepexol (10 h) observed. It may be suggested mediated predominantly alpha1-adrenoceptors observed changes biliary were related to inhibition 5’-monodeiodination liver.