Studies in carotenogenesis. 13. The carotenoids of the flower petals of <i>Calendula officinalis</i>

Abstract

follows that the action of BHDB in inhibiting the effect of thyroxine on the oxygen consumption of mice and its opposite action in the case of triiodo- thyronine (Maclagan et al. 1952) cannot have been due to changes in the total excretion rate.They must therefore reflect alterations in the activity of the circulating thyroid hormone, probably con- sequent upon inhibition of deiodination processes.SUMMARY 1.Details are given for a method of preparation from 3:5-diiodo-L-thyronine of triiodothyronine labelled in the 3' position with "1"I.Radioactive triiodothyronine appears to be much more stable in solution at pH 8-9 than labelled thyroxine.2. The labelled compound was injected into rats, with or without simultaneous administration of butyl 4-hydroxy-3:5-diiodobenzoate (BHDB), and the radioactivity of the exereta was measured.3. Administration of BHDB caused a marked reduction in the output of urinary iodide in intact rats after a single injection of labelled triiodo- thyronine at a number of different dose levels.This is interpreted as being due to interference with the deiodination of this compound.