Physiological role of the conversion of T_4 to T_3 and its relationship to phosphorelation in the kidney.
| Project/Area Number |
61570316
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
内科学一般
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| Research Institution | Jichi Medical University |
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Principal Investigator |
ASANO Yasushi Jichi Med. Sch., Professor of Med., 医学部, 教授 (00050500)
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| Co-Investigator(Kenkyū-buntansha) |
MURAYAMA Naoki Jichi Med. Sch., Instructor of Med., 医学部, 助手(研究生) (80182137)
TABEI Kaoru Jichi Med. Sch., Assist. Prof. of Med., 医学部, 講師 (90155234)
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| Project Period (FY) |
1985 – 1988
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1988: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1987: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1986: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | Thyroid hormone / Kidney / T_4.5'-monodeiodinase activity / K-secretion / 蛋白リン酸化 / 甲状腺ホルモン、ナトリウム依存性リン輸送 / 甲状腺ホルモン / 近位尿細管リン輸送 / 近位尿細管カリウム輸送 / ナトリウム依存性リン輸送 / 近位曲尿細管 / サイトゾール / 副甲状腺ホルモン / c-AMP |
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| Research Abstract |
Concerning the localization of T_4 5'-monodeiodinase (5'-DI) activity in rabbit nephron segments, our results indicated that the activities were noted in both proximal convoluted and proximal straight tubules. On the other hand, the activities were not detected in other segments. In addition, we estimated the subcellular distribution of 5'-DI activity. These results indicated that there exists high Km valued 5'-DI (PTU-sensitive) at basolateral membrane and brush border membrane (BBM) and also exists high Km and low Km valued 5'-DI (PTU-insensitive) at microsome in the rabbit kidney. Since 5'-DI is localized exclusively in proximal tubules, we examined whether T_4 deiodination to T_3 is essential for its effect on BBM phosphate (PI) transport. From this study, we showed that T_4 alone can cause the increase in BBM Pi transport and that intrarenal T_4 conversion to T_3 by 5'-DI is not essential for antiphosphaturic effect of thyroid hormones. On the other hand, we also investigated the
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modulatory effect of thyroid hormone on endogenous proteins in proximal tubules which are phosphorylated after parathyroid hormone stimulation. However, we could not demonstrated specific modulatory effect of thyroid hormone on these endogenous proteins in proximal tubules. According to the data obtained from biological studies mentioned above, thyroid hormones seems to affect its physiological action in the proximal tubules. Thus we examined the effect of thyroid hormones in the proximal tubules by in vitro microperfusion. In contrast to the previous study, we demonstrated that in the proximal convoluted tubules, potassium (K) was secreted in normal rabbit tubules in vitro. 24 hours after the treatment of thyroid hormones water transport and transepithelial potential difference showed no change. These findings indicated that thyroid hormones might not stimulate Na-K ATPase in rabbit rpoximal convoluted tubules in 24 hours, however, net potassium flux studies clearly indicated that thyroid hormones significantly suppressed K secretion in proximal convoluted tubules. These findings suggests thyroid hormone may stimulate the K permeability in the basolateral membrane of rabbit proximal convoluted tubules. Less
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Report
(4 results)
Research Products
(19 results)
