Effect of radiation and heat on canine interphase lymphocytes in vitro

The radiation and heat sensitivities of interphase canine peripheral blood lymphocytes were studied in vitro. Their appearance under phase microscopy and trypan blue exclusion was used as criteria for viability. The results of the radiation studies indicated that (1) time in culture affected the expression of radiosensitivity, (2) the lymphocytes were heterogeneous in regard to their sensitivity to radiation induced interphase death, (3) interphase lymphocytes could not accumulate or repair sublethal damage leading to interphase death, (4) the rate of cell death reached a maximum which was independent of dose. The results of the hyperthermia studies showed (1) the D0 of cells heated to 42.50C at a pH of 7.2 to 7.3 was 48 to 90 minutes, (2) thermal tolerance developed after 200 minutes of heating, (3) time in culture affected the expression of heat sensitivity especially in regard to the development of thermal tolerance and (4) the target(s) for heat and radiation induced interphase death were not the same based on morphologic observations. This research provided a basis for more investigations into the variation in radiosensitivity of lymphocyte subpopulations, the development and decay of thermal tolerance in heated interphase lymphocytes, and the effect of combined heat and radiation on interphase death of lymphocytes. These studies may help to understand the effects of these treatment modalities on the cancer patient's ability to immunologically react against residual tumor or distant metastases