Kojiro Shichijo

Further studies on the mechanism of action of trypan blue and related dyes in suppressing thyroid activity in the rat

Abstract Mechanism of action of trypan blue and related diazo dyes in suppressing thyroid activity was studied in the rat. Five dyes tested had variable effects on thyroidal radioiodine uptake; EB had the greatest effect, NB2B no effect, the others intermediate. This decrease of thyroidal radioiodine uptake corresponded roughly to the decrease in serum PBI. Six dyes all augmented in vitro uptake of labeled T4 by human red blood cell in dilute rat plasma, but there was no correlation between the in vivo thyroid suppressing activities of the dyes and their in vitro T4 displacing effects. However, when plasma from dye injected animals was used, there was a correlation between the amounts of T4 available to the red blood cell and dye effect on thyroid activity. By utilizing muscle, liver and pituitary, this dye effect was also produced. It is concluded that the primary effect of diazo dyes on the thyroid is to inhibit TSH release by displacing T4 from the binding sites of plasma proteins. Unlike T4, T3 uptake by the red blood cell did not change or its uptake by the muscle and liver decrease significantly under the influence of diazo dyes. Although a physiologic significance of this apparent difference between T4 and T3 is not known, the mode of action of diaze dyes in displacing thyroid hormones from the plasma is somewhat different from that of several drugs reported by others.

Nonenzymatic deiodination of thyroxine in vitro

Abstract Labeled thyroxine is markedly deiodinated nonenzymatically under room light when thyroxine is incubated in physiologic saline. This nonenzymatic deiodination progresses for at least 7 days and not reversible after adding plasma proteins. The deiodination was activated under light and moderate temperature and was inhibited by plasma proteins and under low temperature or complete darkness. Since similar deiodination was also found when thyroxine was incubated in distilled water obtained from the Pharmacy but not in distilled water made in our laboratory, and since tap water was used in our laboratory and the Pharmacy, tap water is not responsible for the observed effect. The fact that a glass instrument was used to make distilled water in our department and a metal instrument was used in the Pharmacy suggests that some heavy metals might be contaminated during distillation procedure. In support of this, thyroxine was markedly deiodinated in distilled water obtained from the Pharmacy. Nonenzymatic deiodination of thyroxine was inhibited by 8-oxychinolin, DDC, EDTA, cuprizone and o-phenanthroline, the most marked inhibition being produced by 8-oxychinolin and DDC. Although actual presence of heavy metal was not chemically assessed in this experiment, it is suggested that some heavy metals are contaminated during distillation procedure and the metals deiodinated thyroxine in the absence of tissue component.

Effects of novobiocin on pituitary-thyroid axis in the rat and its mechanism

Abstract Graded doses (20 to 60 mg.) of novobiocin were injected subcutaneously daily for varying periods of time, and effects of those injections on thyroid weight, thyroidal radioiodine uptake, organic binding of iodine, thyroidal radioiodine release, blood PBI and thyroxine-plasma protein interaction were studied in the rat. Administration of 20 or 40 mg. novobiocin for 7 days produced a low blood PBI without affecting thyroid weight, thyroidal radioiodine uptake and organic binding of iodine. However, thyroidal radioiodine uptake was suppressed at the beginning of the drug administration but it returned to normal by 2 days. In contrast, large doses of novobiocin for 7 days suppressed thyroidal radioiodine uptake and blood PBI. Since the novobiocin-suppressed thyroidal radioiodine release could be accelerated by the administration of exogenous TSH, and since novobiocin did not suppress adrenocortical and gonadal activity, those transitory and continuous inhibitions of thyroid activity might be produced by a decrease of TSH secretion. Muscle uptake of labeled thyroxine was high in the presence of plasma obtained from novobiocin-treated animals or in the presence of plasma with added novobiocin in vitro. Novobiocin was without effect on muscle uptake of thyroxine in the absence of plasma. Electrophoretic study indicated that novobiocin displaced thyroxine from albumin in vitro. It is suggested that novobiocin produced a low blood PBI by displacing thyroxine from albumin. The transitory inhibition of thyroid activity produced by small doses of novobiocin suggests the pattern reaching a new equilibrium in which thyroxine-plasma protein interaction is impaired. A new equilibrium may not be established by 7 days when large doses of novobiocin are administered in the rat.

Effect of cold on plasma protein-thyroxine interaction in the guinea pig

Abstract In an attempt to study a possible alteration in the interaction of protein and thyroxine of animals exposed to cold, the uptake of labeled thyroxine by muscle was measured in the presence of plasma from control guinea pigs and those exposed to the cold. The uptake of labeled thyroxine was less in the presence of control plasma than in the presence of plasma obtained from animals exposed to the cold. The magnitude of this response to cold depends largely upon the severity of the cold. Plasma albumin decreased significantly in animals exposed to cold. TSH significantly augmented the uptake of labeled thyroxine by muscle in the presence of plasma, but ACTH was without effect in this system. Epinephrine and norepinephrine did not alter the uptake of labeled thyroxine by muscle in vitro in the presence of plasma. It is suggested that more free thyroxine is available to cells due to a lower binding affinity of plasma protein for thyroxine produced by a decrease of plasma albumin in animals exposed to cold. An increase of circulating TSH may play an additional role for an increase of free thyroxine in animals exposed to the cold, possibly by altering protein-thyroxine interaction.

Effects of epinephrine and chemically related compounds on enzymatic deiodination of thyroxine, triiodothyronine, monoiodotyrosine and diiodotyrosine in vitro

In an attempt to study thyroid hormone and catecholamine interaction, in vitro effects of epinephrine and chemically related compounds (norepinephrine, asthpul, aldomet, alotec, effortil and ephedrine) on deiodination of thyroxine and triiodothyronine by muscle homogenates or slices of muscle and liver, and on deiodination of monoiodotyrosine and diiodotyrosine by liver slices have been studied in complete darkness. I 131 -labeled thyroxine and triiodothyronine were deiodinated in the presence of muscle homogenate and of slices of muscle and liver during 2 hours incubation, but not in the absence of muscle homogenate or in the presence of boiled homogenate. Epinephrine, within the wide dose range used, inhibited deiodination of iodothyronines by muscle homogenate, but oxidized material(s) of epinephrine was without effect. Another 4 compounds (norepinephrine, asthpul, aldomet and alotec) with 2 OH groups at 3 and 4 or 3 and 5 of the benzene ring did also inhibit enzymatic deiodination of iodothyronine. However, 2 compounds (effortil and ephedrine) without 2 OH groups failed to affect enzymatic deiodination. In the presence of dilute rat plasma, muscle homogenate failed to deiodinate thyroxine, but it manifested its action when free thyroxine was increased by adding salicylate. Epinephrine inhibited deiodination of thyroxine by muscle homogenate in the presence of dilute rat plasma and salicylate. Epinephrine and another 6 compounds failed to affect deiodination of monoiodotyrosine and diiodotyrosine by liver slices. It is concluded that epinephrine and another 4 chemically related compounds with 2 OH groups at the benzene ring specifically inhibit enzymatic deiodination of thyroxine and triiodothyronine at least in vitro.

3H thymidine autoradiographic studies on the regeneration of gastric mucosa

however, have no clear correlation to the histological findings. Waving, thickening and disorder of mueosal muscle layer was well correspond to the morphological disorder of gastric area. 4. Cases which shows irregular in contour and sparse in density were accompanied with intestinal metaplasia and hypcrplasia of foveolar epithelium in a high rate. 5. Investigating the difference of morphological and histological change between metaplastie group and hyperplastie group without metaplastie change, the former shows more remarkable morphological change and atrophy of pyloric gland with less growth of lymphfollicle and cell infiltration in lamina propria than the latter.

Effect of centrophenoxine hydrochloride on thyroxine metabolism in the rat

Abstract A brain-stimulating compound, centrophenoxine hydrochloride (CH) lowered plasma PBI in thyroidectomized, thyroxine-maintained rats. The in vitro uptake of labeled thyroxine by diaphragm was directly correlated with the amount of CH adde dto plasma. Plasma obtained from CH-treated animals increased the uptake of labeled thyroxine by diaphragm. Addition of CH markedly augmented in vitro uptake of labeled thyroxine by the anterior pituitary, posterior pituitary, anterior hypothalamus and cerebral cortex. In addition, this augmentation of cellular uptake of labeled thyroxine resulted in an increased deiodination of thyroxine in the presence of dilute rat plasma. Two of three monoamineoxidase inhibitors slightly augmented the uptake of labeled thyroxine by the brain, but none of brain-stimulating drugs studied augmented the uptake by the brain in the presence of plasma in vitro. It is suggested that CH interferes with thyroxine-plasma protein interaction and makes more free thyroxine available to the cells. This CH effect largely depends upon the action of p-chlorophenoxyacetic acid, a constituent of CH.

Comparison of the effects of several drugs on tissue uptake of labeled thyroxine and triiodothyronine in the presence of rat plasma in vitro

In an attempt to study the effects of 18 compounds on plasma protein-thyroid hormone interaction, pituitary, liver and muscle uptakes of labeled thyroxine and triiodothyronine were studied in the presence of rat plasma and the drugs. In addition to the known compounds (DNP, 6 congeners of salicylate, sodium lauryl sulfate [SLS], trypan blue and novobiocin), chloroquine diphosphate, bromophenol blue, calcium salicylate and rose bengal have been shown to displace thyroxine from the binding sites of rat plasma, as evidenced by the fact that tissue uptake of labeled thyroxine was high in the presence of those drugs. The increase of thyroxine uptake was greatest in the pituitary, intermediate in the muscle, and least in the liver. When relative potencies of those drugs were roughly calculated as the percentage of their control uptake, DNP, salicylate and SLS had the strongest, trypan blue and chloroquine diphosphate had the intermediate, and rose bengal, novobiocin and BPB had the least effect on plasma protein-thyroxine interaction in the rat. On the other hand, quinine hydrochloride and resorcinol significantly suppressed tissue uptake of labeled thyroxine. DNP, salicylate and SLS augmented the uptake of triiodothyronine by some tissues but their effects were weak. Trypan blue and salicylamide significantly suppressed triiodothyronine uptake by the tissue.

Lack of inhibitory or excitatory effects of sex hormones on the development of normal methylthiouracil-induced goiter in the rat

Abstract To study a possible etiologic role of sex hormones on the development of simple goiter, estradiol benzoate (EB), testosterone propionate (TP), or methyltestosterone (MT) were administered subcutaneously daily for 14 days to normal rats or rats receiving small doses of methylthiouracil (MTU). In agreement with our previous report, it was found that goiter with normal radioiodine uptake followed the intraperitoneal administration of small doses of MTU. It was also shown that goiter with high radioiodine uptake was produced by large doses of EB (50 or 100 μg.) but not by small doses (1 μg.). Small or large doses of EB have failed to augment the goiter produced by small doses of MTU. Furthermore, unlike the findings in man, large doses of EB failed to increase thyroxine-binding capacity of the plasma proteins in the rat. TP, over a wide range of dose, produced a marked growth of the seminal vesicles, but failed to reduce the size of the normal thyroid or the thyroid stimulated by small doses of MTU. TP also failed to reduce the thyroxine-binding capacity of plasma proteins. Although the data on the rat do not support the hypothesis that sex hormones affect the development of goiter by altering the thyroxine-binding capacity of plasma proteins, the data are not necessarily applicable to the physiology of the human thyroid because of differences in thyroxine-binding proteins between man and rat.