CHANGES OF PINEAL N-ACETYLTRANSFERASE ACTIVITY IN GAMMA-IRRADIATED RATS

Male Wistar rats were exposed to whole body irradiation with 14.35 Gy gamma rays after the adaptation to light/dark cycle (LD 12:12). Three groups of rats were examined: A) rats irradiated in the night and plac ed in the 12 h LD cycle again, B) rats irradiated in the day-time and placed In the 12 h LD cycle, and C) rats irradiated in the night and k ept in constant darkness. All analyses were carried out in the dark. R adiation enhanced the activity of pineal N-acetyltransferase 3-4 days after exposure in all groups, in the C group significantly on the 4th day. Different light regimens during and after irradiation did not to affect the activity of this key enzyme of melatonin synthesis substant ially.