Direct quantitative estimation of several iodothyronines in rat bile by radioimmunoassay and basal data on their biliary excretion

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

“…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). From this it was concluded that the biliary excretion of tri-and di-iodothyronines predominantly reflects the rate of their metabolic produc¬ tion in the liver, their hepatic clearance from plasma being ordinarily negligible.…”

“…and thus the concentration of total (i.e. conjugated plus unconjugated) iodothyronines was estimated by a radioimmunoassay using specific antisera prepared in this laboratory (Földes et al 1982). Half of the bile was used for the estimation of each compound compared with that found by Földes et al (1982) to prevent a possible interfering effect of bile acids with the radioimmunoassay.…”

“…conjugated plus unconjugated) iodothyronines was estimated by a radioimmunoassay using specific antisera prepared in this laboratory (Földes et al 1982). Half of the bile was used for the estimation of each compound compared with that found by Földes et al (1982) to prevent a possible interfering effect of bile acids with the radioimmunoassay. The results are expressed as total excretion of individual iodothyronines per 2 h. The bile samples for each group were analysed in the same assay, the between-assay variation being less than 15%.…”

“…Measuring changes in the biliary excretion of iodothyronines has been found to be a suitable method for studying acute changes of iodothyronine metab¬ olism in the rat liver in vivo (Feldes, Langer, Straussová et al 1982Langer, Suzuki, Kakegawa et al 1985;Langer, Földes & Gschwendtová, 1988).…”

Acute changes in biliary excretion of reverse triiodothyronine in rats after insulin-induced hypoglycemia: effect of glucose, verapamil, cycloheximide and actinomycin D

“…The concentration of T4 in rat bile is approximately the same as in plasma, although the concentration of other iodothyronines is four to eight times higher than that in plasma (8). Biliary excretion of tri-and diiodothyronines thus predominantly reflects the rate of their metabolic production in the liver, their hepatic clearance from plasma being negligible ordinarily.…”