Thyroxine 5-deiodinase in human brain tumors
| Autor: | Kouki Mori, Yoshihiko Aizawa, Kyou Kikuchi, Keishi Abe, Nobuko Kaise, Takamasa Kayama, Yoshinori Kiso, Katsumi Yoshida, Hiroshi Fukazawa |
|---|---|
| Rok vydání: | 1993 |
| Předmět: |
Adult
Male medicine.medical_specialty Triiodothyronine Reverse Endocrinology Diabetes and Metabolism Thyroxine deiodinase Clinical Biochemistry Brain tumor Biology Iopanoic Acid Iodide Peroxidase Biochemistry Iopanoic acid Endocrinology Internal medicine Glioma medicine Humans Child neoplasms Incubation Aged Aurothioglucose Brain Neoplasms Biochemistry (medical) Infant Middle Aged medicine.disease nervous system diseases Dithiothreitol Child Preschool Female Thyroxine 5-deiodinase Oligodendroglioma medicine.drug |
| Zdroj: | The Journal of Clinical Endocrinology & Metabolism. 77:1198-1202 |
| ISSN: | 1945-7197 0021-972X |
| Popis: | To determine whether human brains contain deiodinating pathways, we studied the activity of T4 5-monodeiodinase (5-D) in 20 human brain tumors obtained intraoperatively, including astrocytoma (10), meningioma (4), oligodendroglioma (2), glioblastoma (2), medulloblastoma (1), and malignant lymphoma (1). Mitochondrial-microsomal fractions prepared from these tumor tissues were used as the source of T4 5-D. Each sample was incubated with 32.2 nmol/L T4 and 30 mmol/L dithiothreitol at 37 C for 90 min. T4 5-D activity was measured by the production of rT3 from T4 with a RIA. T4 5-D activity was found in 6 of 10 astrocytomas, 2 oligodendrogliomas, 1 of 2 glioblastomas, and 1 malignant lymphoma. This activity depended on protein concentration, incubation time, incubation temperature, and pH of the incubation mixture. It was also heat labile. T4 5-D was not inhibited by 1 mmol/L propylthiouracil, but was inhibited by iopanoic acid and aurothioglucose in a dose-dependent manner. The apparent Km and maximum velocity for T4 5-D at 30 mmol/L dithiothreitol were 106.6 nmol/L and 22.7 pmol/mg protein.h, respectively. These data suggest that human gliomas (and probably malignant lymphomas) contain T4 5-D activity, which is similar to type III enzyme activity in the rat. T4 5-D may regulate the intracellular concentration of thyroid hormone in gliomas. |
| Databáze: | OpenAIRE |
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