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

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

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.

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.