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

Abstract

Biliary excretion of total (i.e. conjugated plus unconjugated) 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.

Effect of the glycogenolytic gluconeogenetic hormones, glucagon, vasopressin and angiotensin II, on biliary excretion of iodothyronines in rats is possibly related to the inhibition of 5′-monodeiodination in the liver

“…The decrease of biliary excretion of T4 and T3 at subsequent time-intervals as found in controls and also in hormone-infused groups was in agreement with previous observations (Földes et al 1983;Langer, Suzuki, Kakegawa et al 1985;Langer, Földes & Gschwendtová, 1988). This may be due to the stress of operation, pro¬ longed anaesthesia or some other unknown factors.…”

“…We have been able to demonstrate such a phenomenon only in a few individual experiments using either a higher dose of the compound examined (Langer et al 1985) or a small loading dose of T4 injected before the experiment . In contrast, however, the repeatedly increased rT3 excretion appears to be a useful index of hepatic changes of iodothyronine metabolism (Földes et al 1983;Langer et al 1985 and similar observations were made in the present experiments. The concentration of T4 in rat bile was previously found to be approximately the same as that in plasma, although the concentration of other iodothyronines was four to eight times higher than in plasma (Földes et al 1982).…”

Acute Decrease in Vitellogenin Synthesis by deprivation of food and Water in Laying Hens.

“…Transfer of the proteins onto nitrocellulose by incubation with PBS containing 0.05% Tween-20 and 3% bovine serum albumin, and with the diluted antiserum (1: 1, 000 Hormone assays Serum iodothyronine concentrations such as T4, T3 and rT3 were assayed by appropriate radioimmunoassay (RIA) systems. Antisera to T4 and T3 were supplied by M. Suzuki (Suzuki and Suzuki, 1981), while antiserum to rT3 was supplied by P. Langer (Foldes et al, 1982). The serum concentration of the iodothyronines was corrected according to the crossreactivity.…”

Studies on In-Vivo Capacity of Thyroxine Deiodinating System in Rat Liver: Biliary Excretion of Several Iodothyronines after Increasing Loading Doses of Thyroxine

“…and thin polyethylene tubings (PE 50, Clay Adams, Parsipanny, N.J.) were inserted into the bile duct and femoral vein. The experiment was started by the injection of thyroxine into the venous cannula and since this time the bile was continuously collected for three 2-hr periods into pre-weighed vials containing a small amount of Tapazol (Lilly) as described previously (Földes et al, 1982(Földes et al, , 1983Langer et al, 1982Langer et al, , 1984a. After 6 hr of bile collection the animals were sacrificed by withdrawal of blood from abdominal aorta and the plasma thus obtained was used for the estimation of iodothyronines.…”

“…Previously we developed radioimmunoassay methods for the estimation of several iodothyronines in bile (Földes et al, 1982) and found that the iodothyronines from the liver were apparently preferentially excreted to the bile which supports the view that the estimation of biliary excretion of iodothyronines reflects the process of thyroxine deiodination in the liver very closely and may be used as a suitable method for the study of various effects on this metabolic pathway in vivo (Langer et al, 1982, !l984a, h;Földes et al, 1983).…”