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  • Author: N Matsuzaki x
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H-T Ma, S Reuse, N Koibuchi and S Matsuzaki

Abstract

Polyamines such as putrescine, spermidine and spermine have been thought to play an important role in thyroid growth induced by goitrogens. Reduced biosynthesis of these polyamines might play a role in the antigoitrogenic effects of excess iodide. This study was designed to examine the effect of potassium iodide (KI) on ornithine decarboxylase (ODC), a rate-limiting enzyme in the biosynthesis of polyamines. Thyroidal ODC activity, protein content and mRNA were increased in rats made hypothyroid by 10 days of propylthiouracil treatment. The increase in ODC activity was suppressed after subcutaneous injection of KI (13 mg/kg body weight); the apparent half-life of ODC activity after the treatment was estimated to be 19 min and the maximum suppression (90%) was seen 60 min after the treatment. On the other hand, administration of iodine-containing compounds including l-thyroxine, l-di-iodotyrosine, amiodarone, iopanoic acid and erythrosine showed no significant effect on ODC activity. The inhibitory effect of excess iodide was not reversed by pretreatment with dibutyryl cAMP and theophylline. The amount of immunoreactive ODC protein was reduced by iodide treatment (40%). However, the decrease was not as great as the decrease in ODC activity (90%). No significant change in thyroidal ODC mRNA content was seen 1 and 3 h following KI treatment. These results suggest that excess iodide reduces ODC activity in the rat thyroid gland by a post-transcriptional mechanism.

Journal of Endocrinology (1996) 150, 369–376

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N. Koibuchi, S. Matsuzaki, H.-T. Ma, M. Sakai and S. Yamaoka

ABSTRACT

The effect of testosterone on the activity of ornithine decarboxylase (ODC), its protein level and immunocytochemical distribution were examined in the mouse kidney. Male BALB C mice at 8 weeks of age were used throughout. Fourteen hours before death, they received a subcutaneous injection of testosterone (1 mg/animal) or solvent to measure renal ODC activity or to detect the distribution of ODC immunoreactivity in the kidney. Renal ODC activity and the content of the enzyme were markedly increased after testosterone treatment. Histologically, few cells that were obviously immunoreactive to ODC were observed in the control animals and in the testosterone-treated animals a marked increase in ODC immunoreactivity was observed only in the cortex. ODC immunoreactive cells were located diffusely in the proximal tubule. In the pars recta, cells were stained weakly and homogeneously, while in the pars convoluta, the luminal surface of the cells showed stronger immunoreactivity. Moreover, many granule-like particles that were strongly ODC immunoreactive were observed inside the lumen of the pars convoluta. These results show that testosterone treatment induces an increase in ODC content in certain cells located in the proximal tubule of the cortex.

Journal of Endocrinology (1993) 136, 85–89

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T Okada, N Matsuzaki, K Sawai, T Nobunaga, K Shimoya, K Suzuki, N Taniguchi, F Saji and Y Murata

Chorioamnionitis has been shown to be one of the most important factors in inducing preterm delivery. The present study was undertaken to examine the effects of chorioamnionitis on placental endocrine functions. Preterm placentas with histologic chorioamnionitis produced smaller amounts of human chorionic gonadotropin (hCG) and human placental lactogen (hPL) than those without chorioamnionitis (P < 0.001). To examine the mechanism involved in the suppression of placental endocrine functions induced by chorioamnionitis, we initially confirmed the expression of lipopolysaccharide (LPS) receptor, i.e. the CD14 molecule, on trophoblasts by Northern blot analysis and immunohistochemistry. We then stimulated purified trophoblasts with LPS, which is the major agent which induces inflammatory responses in the host via the LPS receptor. The trophoblasts stimulated with LPS produced reduced amounts of hCG, hPL, and progesterone in a time- and dose-dependent fashion in spite of the induced manganese-superoxide dismutase (SOD) synthesis. Stimulation of trophoblasts with hypoxanthine and xanthine oxidase resulted in suppressed hCG production, while the simultaneous addition of SOD into the culture medium reversed the suppression of hCG production. LPS in the placenta with chorioamnionitis might directly stimulate trophoblasts through the LPS receptor (CD14), thus reducing placental endocrine functions. Superoxide anions which exogenously act on trophoblasts might be generated by simultaneous stimulation of neutrophils and monocytes at the feto-maternal interface by LPS, and additively reduce placental endocrine functions.