Thyrotropin regulation of malic enzyme in FRTL5 rat thyroid cells
| Autor: | Leonard D. Kohn, Aimee D. Kohn, Salvatore M. Aloj, Domenico Grieco, Vera M. Nikodem |
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| Přispěvatelé: | Aloj, SALVATORE MARIA, Grieco, Domenico, Kohn, A. D., Nikodem, V. M., Kohn, L. D. |
| Jazyk: | angličtina |
| Rok vydání: | 1990 |
| Předmět: |
DNA Replication
endocrine system medicine.medical_specialty endocrine system diseases Thyroid Gland Malic enzyme 8-Bromo Cyclic Adenosine Monophosphate Thyrotropin Cycloheximide Biology Second Messenger Systems chemistry.chemical_compound Endocrinology Malate Dehydrogenase Internal medicine Gene expression medicine Animals Malic enzyme activity RNA Messenger Molecular Biology Cells Cultured chemistry.chemical_classification DNA synthesis Cell growth General Medicine Molecular biology Actins Stimulation Chemical Rats Enzyme chemistry Enzyme Induction Dactinomycin Thymidine Cell Division hormones hormone substitutes and hormone antagonists Half-Life |
| Popis: | TSH-induced increases in malic enzyme mRNA levels in FRTL-5 rat thyroid cells are paralleled by increases in malic enzyme activity and are mimicked by 8-bromo-cAMP. Apparent approximately 4 h after TSH challenge and maximal after 16 h, they decline by 24 h and are at basal levels by 48 h. The increase occurs in the absence of a measurable effect of TSH on DNA synthesis related to cell growth, since [3H] thymidine incorporation into DNA is still at basal levels 24 h after TSH challenge and is maximal only at 48 h. A protein(s) whose formation is inhibited by cycloheximide appears to be critical to the ability of TSH to increase malic enzyme mRNA levels. Thus, cycloheximide given 30 min before TSH prevents the hormone-induced increase in malic enzyme mRNA; also, when given 24 h after TSH, cycloheximide accelerates the loss of the TSH-induced increase in malic enzyme mRNA. In neither case does cycloheximide affect beta-actin mRNA levels. A second factor(s) whose formation is prevented by actinomycin-D appears to be important for the decrease in malic enzyme mRNA levels seen 24 and 48 h after TSH challenge. Thus, in experiments in which it is given 24 h after TSH, actinomycin-D preserves the hormone-induced increase in malic enzyme mRNA levels rather than accelerating the decrease, as does cycloheximide. In the same experiment, beta-actin mRNA levels decrease to less than 10-20% of control values over the same period; this factor also, therefore, appears to exhibit some degree of specificity.(ABSTRACT TRUNCATED AT 250 WORDS) |
| Databáze: | OpenAIRE |
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