報告書番号

L05016

タイトル（和文）

低線量率放射線が造血幹細胞および末梢血に及ぼす長期的影響

タイトル（英文）

Effects for hematopoietic stem cells and peripheral blood by low dose-rate irradiation

概要 （図表や脚注は「報告書全文」に掲載しております）

1.2mGy/hrの線量率で長期にわたって照射したC57BL/6Nマウスの末梢血球数および造血幹細胞の数を分析した。赤血球の数は照射期間が40日の時点で一時的に減少したが、照射から140日までには回復していた。一方、KSL細胞の中でもCD34と呼ばれるタンパク質を持たない細胞は未分化な造血幹細胞として知られているが、低線量率照射の影響を受けなかった。これらの結果は、低線量率照射によって末梢血および多能性前駆細胞の数が一時的に減少しても、最も重要な幹細胞が影響を受けないために、低線量率照射下においても長期的には造血能が保たれていることを示している。

概要 （英文）

Hematopoietic system is one of the radiosensitive tissues. It is known that a irreversible injury for blood cells is induced by a high dose-rate radiation. But the effects of the low dose-rate radiation on the hematopoietic system have not been revealed. First of all, we evaluated the number of blood cells induced by 0.5 Gy of the low dose-rate (1.2 mGy/hr) or the high dose-rate (0.45 Gy/min) radiation on the number of peripheral blood cells: a significant decrease of erythrocytes was observed at the high dose-rate while no reduction of the number of erythrocytes was shown at the low dose-rate. Secondary, the variation of the number of peripheral blood cells and hematopoietic stem cells in C57BL/6N mice were analyzed after whole body irradiation at low dose-rate (1.2 mGy/hr). The number of erythrocytes was transiently decreased when the low dose-rate irradiation reached 42 days (1 Gy total). But it recovered by the time reached 140 days (3 Gy total). The CD34- KSL cells, which were known for the undifferentiated hematopoietic stem cells were not decreased under the low dose-rate condition. These results indicated that the low dose-rate irradiation induces transient decreasing of the peripheral blood cells and multipotential progenitor cells but did not affect an ability of hematopoiesis of hematopoietic stem cells in the longer term.

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