ステロイドホルモンの核酸代謝に及ぼす影響
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概要
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The author studied on the DNA and RNA metabolism in tissue culture of FL cells by means of <SUP>3</SUP>H-Thymidine (<SUP>3</SUP>HTDN) and <SUP>3</SUP>H-Uridine (<SUP>3</SUP>HUDN) microautoradiography. The generation time of the cells was determined by measuring the cell ccncentration at various times with a hemocytometer. <BR>1) FL cells were exposed to prednisolone or 4-chlorotestosterone acetate, with the concentration of 10μg/cc for 24 hours, and then to <SUP>3</SUP> HTDN 0.5 μC/cc for 26 hours with steroid hormones. <BR>A period of active synthesis of DNA (S period) and a premitotic non-synthetic period (G<SUB>2</SUB> period) were obtained from metaphase grain counts as follows : <BR>Tg G<SUB>1</SUB> S G<SUB>2</SUB> m <BR>Control culture 19 hrs 6.5 7.0 5.0 0.5 <BR>Pred.-treated culture 31 13.5 9.5 7.0 1.0 <BR>4Cl-TA-treated culture 24 9.7 7.5 6.0 0.8 <BR>Tg : Generation time <BR>G<SUB>1</SUB> : a postomitotic non-synthetic period m : mitosis time <BR>The percentage of labelled interphase nuclei measured each hour after the addition of <SUP>3</SUP>HTDN should give an independent value of the S period by a mathematical treatment for exponentially multiplying cultures. <BR>In this method, the mean value obtained for S period was 5.0 hours in the control culture, 7.3 hours in prednisolone-treated FL cells and 5.8 hours in 4-chlorotestosterone-treated FL cells. <BR>The length of the S period was prolonged in prednisolone-treated FL cells in both methods, and prolongation of the G<SUB>1</SUB> period was more remarkable. <BR>2) Two types of experiments on RNA metabolism were performed. In the first, FL cell monolayers were exposed to steroid hormones, 10 μg/cc for 24 hours, and then to <SUB>3</SUB>HUDN 1 μC/cc for 2 hours. <BR>In the prednisolone-treated cultures the total uptake of radioisotope into nucleus, nucleolus and cytoplasm were gradually decreased after incubation with <SUP>3</SUP>HUDN for 1 hour ; concurrently the incorporation of <SUP>3</SUP>HUDN into acid insoluble compounds (mainly RNA) was depressed. But the nucleolar incorporation was active. <BR>In the 4-chlorotestosterone acetate-treated cultures the total uptake of radioisotope was slightly decreased, but <SUP>3</SUP>HUDN were incorporated into RNA alike in the control cultures. <BR>Accumulation of <SUP>3</SUP> HUDN in the acid soluble compounds dropped in the prednisolone-treated cultures more than in the control cultures. In the latter, the accumulation of <SUP>3</SUP>HUDN in the nucleus was maximum after incubation with <SUP>3</SUP>IUDN for 90 minutes. On the other hand, in the former, <SUP>3</SUP> HUDN was accumulating still more. <BR>3) In the second type of experiment, FL cells were exposed to <SUP>3</SUP>HUDN 1 μC/cc for 1 hour to allow for the incorporation into cellular RNA, then a new medium containing 50 μg/cc non-radioactive uridine and 10 μg/cc prednisolone were added, and the cultures were successively incubated for 3 hours. <BR>The incorpoation into the cytoplasm of radioisotope, that had been present in acid soluble compounds in the nucleus or in the cytoplasm prior to addition of the prednisolone, diminished to some extent in the prednisolone-treated cultures.
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