X線照射에 따르는 Deoxycytidineuria와 CdR-aminohydrolase의 活性變化와의 連關性

Correlation between Deoxycytidineuria and CdR-aminohydrolase Activity following X-Irradiation

생쥐에 400 및 800 R의 X線을 一時全身照射한 뒤, 몇가지 臟器에서 Dische 陽性物質의 放出量과 CdR-aminohydrolase의 活性變化 및 尿중의 CdR量을 照射후의 時間經過에 따라 측정하여 放射線照射후 deoxycytidineuria의 增加機構의 一面을 究明하려고 시도했다. CdR-aminohydrolase의 活性度는 照射후 1時間째에 小腸과 肝에서 顯著한 감소를 보였으며, 5$\\sim$12시간 사이에 정상水準으로 복귀되었다가 3日째에 最大의 증가를 나타냈다. 한편, 脾臟과 血液의 경우는 對照群과 照射群에서 모두 극미한 活性만이 관찰되었다. Dische 陽性物質의 放出量은 小腸의 경우 照射후 3$\\sim$12시간 사이에 증가를 보였으며 6$\\sim$9시간에 最大値를 나타냈다. 이에 반해서 肝, 脾臟 및 賢臟의 경우는 小腸에 비해 1/20 이하에 불과하였으며, 이들 조직은 照射후 증가하는 deoxycytidineuria에 직접 寄與하지는 않는 것으로 생각된다. Deoxycytidineuria는 照射후 9$\\sim$12시간에 最大値를 보였는데, 이의 相當量이 小腸에 연유하는 것으로 믿어지고, 특히 小腸의 CdR-aminohydrolase의 活性度의 변화와 깊은 關連이 있는 것으로 생각된다. 즉 放射線照射후 DNA分解産物중 CdR이 CdR-aminohydrolase의 活性이 격감하는 시기에 조직으로부터 血液으로 放出되고, 血液내에서는 별다른 量的변화를 거치지 않고 尿에 섞여 排泄되는 것으로 思料된다.

This work was undertaken to elucidate some aspects of mechanisms underlying the increased deoxycytidineuria following irradiation in the mice, by observing Dische-positive substances liberated from thissues, the activity of CdR-aminohydrolase of tissues and the CdR excreted in the urine at various times after single whole-body exposure to 400 and 800 R of X-rays. The activity of CdR-aminohydrolase declined markedly at 1 hour in the small intestine and liver, followed by a gradual rise reaching a maximum at 3 days after irradiation. In the case of the spleen and blood, however, only a trace of activity was observed in the control and irradiated animals. The amount of Dische-positive substance liberated from the small intestine postirradiation was elevated from 3 to 12 hours, showing a maximum during 6 to 9 hours after irradiation. On the contrary, the activity of the enzyme in the liver, spleen and kidney was less than one twentieth that of the small intestine, suggesting a prediction that these organs are not attributable to the increased deoxycytidineuria. A maximum deoxycytidineuria was exhibited at 9-12 hours period, attributed a large amount of CdR to the small intestine, which might correlate with the change in the CdR-aminohydrolase activity. Radiation-induced CdR seems to be liberated from the small intestine into the blood when the CdR-aminohydrolase activity declines abruptly. Then, the CdR is rapidly subjected to a filtration in the kidney without undergoing a further degradation pathway in the blood.