Diphenylhydantoin Stimulates the Intrapituitary Conversion of Thyroxine to Triiodothyronine in the Rat
| Autor: | Laura F. Cageao, Angel A. Zaninovich, Jorge A. Ceppi, Ruben J. Boado |
|---|---|
| Rok vydání: | 1992 |
| Předmět: |
Male
endocrine system medicine.medical_specialty Pituitary gland endocrine system diseases Endocrinology Diabetes and Metabolism Deiodinase Radioimmunoassay Feedback Cellular and Molecular Neuroscience Endocrinology Serum thyroxine Internal medicine medicine Animals Rats Wistar Triiodothyronine biology Endocrine and Autonomic Systems Chemistry technology industry and agriculture Metabolism Rats Thyroxine medicine.anatomical_structure Phenytoin Pituitary Gland biology.protein lipids (amino acids peptides and proteins) hormones hormone substitutes and hormone antagonists |
| Zdroj: | Neuroendocrinology. 56:453-458 |
| ISSN: | 1423-0194 0028-3835 |
| DOI: | 10.1159/000126261 |
| Popis: | Treatment of normal rats with diphenylhydantoin (DPH) decreases serum thyroxine (T4) and triiodothyronine (T3) levels without the anticipated rise in serum thyrotropin (TSH). The present work has studied the intrapituitary conversion of T4 to T3 in male Wistar rats, 200-250 g body weight (BW), treated with DPH 5 mg/100 g BW/day for 8 days. A tracer dose of 3',5'-[125I]T4 (150 microCi) was injected intravenously, and 2 h later hypophyses were removed and homogenized individually at 4 degrees C in ice-cold PBS buffer (pH 7.4). T4 and T3 were extracted in 400 microliters n-butanol:2 N HCl (9:1) and chromatographed in tertiary amyl alcohol:hexane: 1 N ammonia (5:1:6). In 11 untreated control rats, [125I]T3 generated from [125I]T4 deiodination was 35 +/- 6% and intact [125I]T4 was 49 +/- 9% of total chromatographic radioactivity. In 11 DPH-treated rats [125I]T3 increased (p0.001) and [125I]T4 decreased (p0.02). The DPH effect was blocked in rats treated for 2 days with iopanoic acid 10 mg/100 g BW, though blocking was not seen in rats treated with half the dose of iopanoic acid. In normal rats receiving supplemental doses of T4 (2 micrograms/100 g BW/day for 8 days), DPH similarly increased pituitary 5'-deiodination. Administration of propylthiouracil (PTU) to T4-supplemented rats had no effect on pituitary 5'-deiodination of T4, whereas the addition of DPH to PTU treatment increased [125I]T3 production (p0.01). Serum T4 (p0.001) and T3 (p0.01) were decreased after DPH therapy, while serum and pituitary TSH were not altered.(ABSTRACT TRUNCATED AT 250 WORDS) |
| Databáze: | OpenAIRE |
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