The effect of chronic radiation on the humoral immune response of rainbow trout (Onchorhynchus mykiss Walbaum).

Two separate experiments have examined the effect of exposing rainbow trout to chronic gamma-radiation, commencing immediately after fertilization. In experiment 1 the period of exposure extended for 20 days with groups receiving mean dose rates of 1.87, 3.73 and 9.03 mGy h-1, and mean total accumulated doses of 0.83, 1.66 and 4.01 Gy respectively. At 5 months of age fish were tested for specific antibody response to dinitrophenol coupled to keyhole limpet haemocyanin (DNP-KLH) and there was no significant difference in titre between irradiated groups and unirradiated controls. In experiment 2 the exposure period was extended to 246 days from fertilization. Mean dose-rates to the three groups used were the same as in the first experiment until hatching at 21 days and then lower with rates of 0.99, 1.9, and 4.66 mGy h-1 to the free-swimming fish. The mean total accumulated doses over the whole irradiation period were 5.43, 10.53 and 25.43 Gy respectively. The antibody response to DNP-KLH was significantly lower in trout receiving the highest dose-rate when compared with those of unirradiated controls or the lowest dose-rate group. The significance of these results is discussed in relation to radiation levels in areas of radioactive waste disposal, and results from a similar study published previously.