20 Normal glands obtained from euthyroid subjects at autopsy were analysed for total iodine (Tl), PBl, L-thyroxine (T4), 3,3',5-triiodothyronine (T3), 3,3',5'-triiodothyronine (rT3), 3,3'-diiodothyronine (T2) after pronase hydrolysis. The mean Tl was 325.1+-47.2 micrograms/g wet tissue, giving a total iodine per gland of 10.01 mg. Pretreatment of iodine containing X-ray drugs in 8 patients did not significantly affect these results with the exception of Lipiodol. The mean T4, T3 and T2 values were 93.0+-23.1 micrograms/g, 5.25+-0.99 micrograms/g, 5.54+-1.05 micrograms/g and 0.60+-1.19 micrograms/g, respectively. In contrast to goitrous tissue, normal thyroid tissue showed no dependence of the T4/T3 ratio on the Tl. Compared with goitrous tissue PBI consisted of much more T4-l in normal tissue. The corresponding values were 47.7+-11.8% and 12.7+-3.4%, respectively. A positive relationship was found between Tl and T4, T3, rT3 but not with T2. The rT3 concentration corresponds to that of T3 in a remarkable way. The ratios of T3 or rT3 were similar, suggesting that thyroidal T3 and rT3 production is a random process. T2 represents only 0.73% of T4-l. Our results in normal thyroid tissue clearly show that the difference in iodine concentrations is only one factor among others in comparison to goitrous tissue.

Rythmes circadiens du pouls, de la pression arterielle, des exen;tions urinaires en 17-T 4/T 3 Ratio in Autonomous Adenomas

The deiodinaton of 1311-labeled thyroxine and trüodothyronine by red ceU membranes prepared from healthy persons was examined. Vnder the experimental conditions (pH 6.0, 32°C) 0.5 mg membranes deiodinated 1.6 m", moles triiodothyronine in 30 min. Iodide and a substance with an Rf of 0 in paper chromatography were the only radioactive deiodination products. The membrane system was shown to be heat stabile and dependent on an alkali labile nondialyzable factor. Iodide release is linked to membrane partieles and can be demonstrated even after lipid extraction of the ghosts. The deiodinating system is highly active without the addition of any activators and is characterized by time dependency and a pH optimum of 6.0. Stimulators of the reaction are oxygen, Ca 2 +, Cu 2 + and fructose 1,6-diphosphate. A peroxidative mechanism catalyzed by traces of hemoglobin and a non~nzymatic FMN 1ight-induced iodide release could be exeluded. The membrane-linked deiodination might play an important role in the peripheral metabolism of thyroid hormones.

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